doctest
— 测试交互 Python 范例
¶
源代码： Lib/doctest.py
doctest
module searches for pieces of text that look like interactive Python sessions, and then executes those sessions to verify that they work exactly as shown. There are several common ways to use doctest:
这里是完整但很小的范例模块：
"""
This is the "example" module.
The example module supplies one function, factorial(). For example,
>>> factorial(5)
120
"""
def factorial(n):
"""Return the factorial of n, an exact integer >= 0.
>>> [factorial(n) for n in range(6)]
[1, 1, 2, 6, 24, 120]
>>> factorial(30)
265252859812191058636308480000000
>>> factorial(-1)
Traceback (most recent call last):
...
ValueError: n must be >= 0
Factorials of floats are OK, but the float must be an exact integer:
>>> factorial(30.1)
Traceback (most recent call last):
...
ValueError: n must be exact integer
>>> factorial(30.0)
265252859812191058636308480000000
It must also not be ridiculously large:
>>> factorial(1e100)
Traceback (most recent call last):
...
OverflowError: n too large
"""
import math
if not n >= 0:
raise ValueError("n must be >= 0")
if math.floor(n) != n:
raise ValueError("n must be exact integer")
if n+1 == n: # catch a value like 1e300
raise OverflowError("n too large")
result = 1
factor = 2
while factor <= n:
result *= factor
factor += 1
return result
if __name__ == "__main__":
import doctest
doctest.testmod()
If you run
example.py
directly from the command line,
doctest
works its magic:
$ python example.py
$
There’s no output! That’s normal, and it means all the examples worked. Pass
-v
to the script, and
doctest
prints a detailed log of what it’s trying, and prints a summary at the end:
$ python example.py -v
Trying:
factorial(5)
Expecting:
120
ok
Trying:
[factorial(n) for n in range(6)]
Expecting:
[1, 1, 2, 6, 24, 120]
ok
And so on, eventually ending with:
Trying:
factorial(1e100)
Expecting:
Traceback (most recent call last):
...
OverflowError: n too large
ok
2 items passed all tests:
1 tests in __main__
8 tests in __main__.factorial
9 tests in 2 items.
9 passed and 0 failed.
Test passed.
$
That’s all you need to know to start making productive use of
doctest
! Jump in. The following sections provide full details. Note that there are many examples of doctests in the standard Python test suite and libraries. Especially useful examples can be found in the standard test file
Lib/test/test_doctest.py
.
The simplest way to start using doctest (but not necessarily the way you’ll continue to do it) is to end each module
M
with:
if __name__ == "__main__":
import doctest
doctest.testmod()
doctest
then examines docstrings in module
M
.
Running the module as a script causes the examples in the docstrings to get executed and verified:
python M.py
This won’t display anything unless an example fails, in which case the failing example(s) and the cause(s) of the failure(s) are printed to stdout, and the final line of output is
***Test
Failed***
N
failures.
，其中
N
is the number of examples that failed.
Run it with the
-v
switch instead:
python M.py -v
and a detailed report of all examples tried is printed to standard output, along with assorted summaries at the end.
You can force verbose mode by passing
verbose=True
to
testmod()
, or prohibit it by passing
verbose=False
. In either of those cases,
sys.argv
is not examined by
testmod()
(so passing
-v
or not has no effect).
There is also a command line shortcut for running
testmod()
. You can instruct the Python interpreter to run the doctest module directly from the standard library and pass the module name(s) on the command line:
python -m doctest -v example.py
This will import
example.py
as a standalone module and run
testmod()
on it. Note that this may not work correctly if the file is part of a package and imports other submodules from that package.
Another simple application of doctest is testing interactive examples in a text file. This can be done with the
testfile()
函数：
import doctest
doctest.testfile("example.txt")
That short script executes and verifies any interactive Python examples contained in the file
example.txt
. The file content is treated as if it were a single giant docstring; the file doesn’t need to contain a Python program! For example, perhaps
example.txt
contains this:
The ``example`` module
======================
Using ``factorial``
-------------------
This is an example text file in reStructuredText format. First import
``factorial`` from the ``example`` module:
>>> from example import factorial
Now use it:
>>> factorial(6)
120
运行
doctest.testfile("example.txt")
then finds the error in this documentation:
File "./example.txt", line 14, in example.txt
Failed example:
factorial(6)
Expected:
120
Got:
720
As with
testmod()
,
testfile()
won’t display anything unless an example fails. If an example does fail, then the failing example(s) and the cause(s) of the failure(s) are printed to stdout, using the same format as
testmod()
.
默认情况下，
testfile()
looks for files in the calling module’s directory. See section
Basic API
for a description of the optional arguments that can be used to tell it to look for files in other locations.
像
testmod()
,
testfile()
’s verbosity can be set with the
-v
command-line switch or with the optional keyword argument
verbose
.
There is also a command line shortcut for running
testfile()
. You can instruct the Python interpreter to run the doctest module directly from the standard library and pass the file name(s) on the command line:
python -m doctest -v example.txt
Because the file name does not end with
.py
,
doctest
infers that it must be run with
testfile()
, not
testmod()
.
For more information on
testfile()
，见章节
Basic API
.
This section examines in detail how doctest works: which docstrings it looks at, how it finds interactive examples, what execution context it uses, how it handles exceptions, and how option flags can be used to control its behavior. This is the information that you need to know to write doctest examples; for information about actually running doctest on these examples, see the following sections.
The module docstring, and all function, class and method docstrings are searched. Objects imported into the module are not searched.
In addition, if
M.__test__
exists and “is true”, it must be a dict, and each entry maps a (string) name to a function object, class object, or string. Function and class object docstrings found from
M.__test__
are searched, and strings are treated as if they were docstrings. In output, a key
K
in
M.__test__
appears with name
<name of M>.__test__.K
Any classes found are recursively searched similarly, to test docstrings in their contained methods and nested classes.
CPython 实现细节： Prior to version 3.4, extension modules written in C were not fully searched by doctest.
In most cases a copy-and-paste of an interactive console session works fine, but doctest isn’t trying to do an exact emulation of any specific Python shell.
>>> # comments are ignored
>>> x = 12
>>> x
12
>>> if x == 13:
... print("yes")
... else:
... print("no")
... print("NO")
... print("NO!!!")
...
no
NO
NO!!!
>>>
Any expected output must immediately follow the final
'>>>
'
or
'...
'
line containing the code, and the expected output (if any) extends to the next
'>>>
'
or all-whitespace line.
The fine print:
Expected output cannot contain an all-whitespace line, since such a line is taken to signal the end of expected output. If expected output does contain a blank line, put
<BLANKLINE>
in your doctest example each place a blank line is expected.
All hard tab characters are expanded to spaces, using 8-column tab stops. Tabs in output generated by the tested code are not modified. Because any hard tabs in the sample output
are
expanded, this means that if the code output includes hard tabs, the only way the doctest can pass is if the
NORMALIZE_WHITESPACE
option or
directive
is in effect. Alternatively, the test can be rewritten to capture the output and compare it to an expected value as part of the test. This handling of tabs in the source was arrived at through trial and error, and has proven to be the least error prone way of handling them. It is possible to use a different algorithm for handling tabs by writing a custom
DocTestParser
类。
Output to stdout is captured, but not output to stderr (exception tracebacks are captured via a different means).
If you continue a line via backslashing in an interactive session, or for any other reason use a backslash, you should use a raw docstring, which will preserve your backslashes exactly as you type them:
>>> def f(x):
... r'''Backslashes in a raw docstring: m\n'''
>>> print(f.__doc__)
Backslashes in a raw docstring: m\n
Otherwise, the backslash will be interpreted as part of the string. For example, the
\n
above would be interpreted as a newline character. Alternatively, you can double each backslash in the doctest version (and not use a raw string):
>>> def f(x):
... '''Backslashes in a raw docstring: m\\n'''
>>> print(f.__doc__)
Backslashes in a raw docstring: m\n
The starting column doesn’t matter:
>>> assert "Easy!"
>>> import math
>>> math.floor(1.9)
1
and as many leading whitespace characters are stripped from the expected output as appeared in the initial
'>>>
'
line that started the example.
By default, each time
doctest
finds a docstring to test, it uses a
shallow copy
of
M
’s globals, so that running tests doesn’t change the module’s real globals, and so that one test in
M
can’t leave behind crumbs that accidentally allow another test to work. This means examples can freely use any names defined at top-level in
M
, and names defined earlier in the docstring being run. Examples cannot see names defined in other docstrings.
You can force use of your own dict as the execution context by passing
globs=your_dict
to
testmod()
or
testfile()
代替。
No problem, provided that the traceback is the only output produced by the example: just paste in the traceback. [1] Since tracebacks contain details that are likely to change rapidly (for example, exact file paths and line numbers), this is one case where doctest works hard to be flexible in what it accepts.
Simple example:
>>> [1, 2, 3].remove(42)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: list.remove(x): x not in list
That doctest succeeds if
ValueError
is raised, with the
list.remove(x):
x
not
in
list
detail as shown.
The expected output for an exception must start with a traceback header, which may be either of the following two lines, indented the same as the first line of the example:
Traceback (most recent call last):
Traceback (innermost last):
The traceback header is followed by an optional traceback stack, whose contents are ignored by doctest. The traceback stack is typically omitted, or copied verbatim from an interactive session.
The traceback stack is followed by the most interesting part: the line(s) containing the exception type and detail. This is usually the last line of a traceback, but can extend across multiple lines if the exception has a multi-line detail:
>>> raise ValueError('multi\n line\ndetail')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: multi
line
detail
The last three lines (starting with
ValueError
) are compared against the exception’s type and detail, and the rest are ignored.
Best practice is to omit the traceback stack, unless it adds significant documentation value to the example. So the last example is probably better as:
>>> raise ValueError('multi\n line\ndetail')
Traceback (most recent call last):
...
ValueError: multi
line
detail
Note that tracebacks are treated very specially. In particular, in the rewritten example, the use of
...
is independent of doctest’s
ELLIPSIS
option. The ellipsis in that example could be left out, or could just as well be three (or three hundred) commas or digits, or an indented transcript of a Monty Python skit.
Some details you should read once, but won’t need to remember:
ValueError:
42
is
prime
will pass whether
ValueError
is actually raised or if the example merely prints that traceback text. In practice, ordinary output rarely begins with a traceback header line, so this doesn’t create real problems.
IGNORE_EXCEPTION_DETAIL
doctest option is specified, everything following the leftmost colon and any module information in the exception name is ignored.
SyntaxError
s. But doctest uses the traceback header line to distinguish exceptions from non-exceptions. So in the rare case where you need to test a
SyntaxError
that omits the traceback header, you will need to manually add the traceback header line to your test example.
For some
SyntaxError
s, Python displays the character position of the syntax error, using a
^
marker:
>>> 1 1
File "<stdin>", line 1
1 1
^
SyntaxError: invalid syntax
Since the lines showing the position of the error come before the exception type and detail, they are not checked by doctest. For example, the following test would pass, even though it puts the
^
marker in the wrong location:
>>> 1 1
File "<stdin>", line 1
1 1
^
SyntaxError: invalid syntax
A number of option flags control various aspects of doctest’s behavior. Symbolic names for the flags are supplied as module constants, which can be
bitwise ORed
together and passed to various functions. The names can also be used in
doctest directives
, and may be passed to the doctest command line interface via the
-o
选项。
3.4 版新增：
-o
command line option.
The first group of options define test semantics, controlling aspects of how doctest decides whether actual output matches an example’s expected output:
doctest.
DONT_ACCEPT_TRUE_FOR_1
¶
By default, if an expected output block contains just
1
, an actual output block containing just
1
or just
True
is considered to be a match, and similarly for
0
versus
False
。当
DONT_ACCEPT_TRUE_FOR_1
is specified, neither substitution is allowed. The default behavior caters to that Python changed the return type of many functions from integer to boolean; doctests expecting “little integer” output still work in these cases. This option will probably go away, but not for several years.
doctest.
DONT_ACCEPT_BLANKLINE
¶
By default, if an expected output block contains a line containing only the string
<BLANKLINE>
, then that line will match a blank line in the actual output. Because a genuinely blank line delimits the expected output, this is the only way to communicate that a blank line is expected. When
DONT_ACCEPT_BLANKLINE
is specified, this substitution is not allowed.
doctest.
NORMALIZE_WHITESPACE
¶
When specified, all sequences of whitespace (blanks and newlines) are treated as equal. Any sequence of whitespace within the expected output will match any sequence of whitespace within the actual output. By default, whitespace must match exactly.
NORMALIZE_WHITESPACE
is especially useful when a line of expected output is very long, and you want to wrap it across multiple lines in your source.
doctest.
ELLIPSIS
¶
When specified, an ellipsis marker (
...
) in the expected output can match any substring in the actual output. This includes substrings that span line boundaries, and empty substrings, so it’s best to keep usage of this simple. Complicated uses can lead to the same kinds of “oops, it matched too much!” surprises that
.*
is prone to in regular expressions.
doctest.
IGNORE_EXCEPTION_DETAIL
¶
When specified, an example that expects an exception passes if an exception of the expected type is raised, even if the exception detail does not match. For example, an example expecting
ValueError:
42
will pass if the actual exception raised is
ValueError:
3*14
, but will fail, e.g., if
TypeError
被引发。
It will also ignore the module name used in Python 3 doctest reports. Hence both of these variations will work with the flag specified, regardless of whether the test is run under Python 2.7 or Python 3.2 (or later versions):
>>> raise CustomError('message')
Traceback (most recent call last):
CustomError: message
>>> raise CustomError('message')
Traceback (most recent call last):
my_module.CustomError: message
注意，
ELLIPSIS
can also be used to ignore the details of the exception message, but such a test may still fail based on whether or not the module details are printed as part of the exception name. Using
IGNORE_EXCEPTION_DETAIL
and the details from Python 2.3 is also the only clear way to write a doctest that doesn’t care about the exception detail yet continues to pass under Python 2.3 or earlier (those releases do not support
doctest directives
and ignore them as irrelevant comments). For example:
>>> (1, 2)[3] = 'moo'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: object doesn't support item assignment
passes under Python 2.3 and later Python versions with the flag specified, even though the detail changed in Python 2.4 to say “does not” instead of “doesn’t”.
3.2 版改变：
IGNORE_EXCEPTION_DETAIL
now also ignores any information relating to the module containing the exception under test.
doctest.
SKIP
¶
When specified, do not run the example at all. This can be useful in contexts where doctest examples serve as both documentation and test cases, and an example should be included for documentation purposes, but should not be checked. E.g., the example’s output might be random; or the example might depend on resources which would be unavailable to the test driver.
The SKIP flag can also be used for temporarily “commenting out” examples.
doctest.
COMPARISON_FLAGS
¶
A bitmask or’ing together all the comparison flags above.
The second group of options controls how test failures are reported:
doctest.
REPORT_UDIFF
¶
When specified, failures that involve multi-line expected and actual outputs are displayed using a unified diff.
doctest.
REPORT_CDIFF
¶
When specified, failures that involve multi-line expected and actual outputs will be displayed using a context diff.
doctest.
REPORT_NDIFF
¶
When specified, differences are computed by
difflib.Differ
, using the same algorithm as the popular
ndiff.py
utility. This is the only method that marks differences within lines as well as across lines. For example, if a line of expected output contains digit
1
where actual output contains letter
l
, a line is inserted with a caret marking the mismatching column positions.
doctest.
REPORT_ONLY_FIRST_FAILURE
¶
When specified, display the first failing example in each doctest, but suppress output for all remaining examples. This will prevent doctest from reporting correct examples that break because of earlier failures; but it might also hide incorrect examples that fail independently of the first failure. When
REPORT_ONLY_FIRST_FAILURE
is specified, the remaining examples are still run, and still count towards the total number of failures reported; only the output is suppressed.
doctest.
FAIL_FAST
¶
When specified, exit after the first failing example and don’t attempt to run the remaining examples. Thus, the number of failures reported will be at most 1. This flag may be useful during debugging, since examples after the first failure won’t even produce debugging output.
The doctest command line accepts the option
-f
as a shorthand for
-o
FAIL_FAST
.
3.4 版新增。
doctest.
REPORTING_FLAGS
¶
A bitmask or’ing together all the reporting flags above.
There is also a way to register new option flag names, though this isn’t useful unless you intend to extend
doctest
internals via subclassing:
doctest.
register_optionflag
(
name
)
¶
Create a new option flag with a given name, and return the new flag’s integer value.
register_optionflag()
can be used when subclassing
OutputChecker
or
DocTestRunner
to create new options that are supported by your subclasses.
register_optionflag()
should always be called using the following idiom:
MY_FLAG = register_optionflag('MY_FLAG')
Doctest directives may be used to modify the option flags for an individual example. Doctest directives are special Python comments following an example’s source code:
directive ::= "#" "doctest:"directive_optionsdirective_options ::=directive_option(","directive_option)\* directive_option ::=on_or_offdirective_option_nameon_or_off ::= "+" \| "-" directive_option_name ::= "DONT_ACCEPT_BLANKLINE" \| "NORMALIZE_WHITESPACE" \| ...
Whitespace is not allowed between the
+
or
-
and the directive option name. The directive option name can be any of the option flag names explained above.
An example’s doctest directives modify doctest’s behavior for that single example. Use
+
to enable the named behavior, or
-
to disable it.
For example, this test passes:
>>> print(list(range(20)))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
Without the directive it would fail, both because the actual output doesn’t have two blanks before the single-digit list elements, and because the actual output is on a single line. This test also passes, and also requires a directive to do so:
>>> print(list(range(20)))
[0, 1, ..., 18, 19]
Multiple directives can be used on a single physical line, separated by commas:
>>> print(list(range(20)))
[0, 1, ..., 18, 19]
If multiple directive comments are used for a single example, then they are combined:
>>> print(list(range(20)))
...
[0, 1, ..., 18, 19]
As the previous example shows, you can add
...
lines to your example containing only directives. This can be useful when an example is too long for a directive to comfortably fit on the same line:
>>> print(list(range(5)) + list(range(10, 20)) + list(range(30, 40)))
...
[0, ..., 4, 10, ..., 19, 30, ..., 39]
Note that since all options are disabled by default, and directives apply only to the example they appear in, enabling options (via
+
in a directive) is usually the only meaningful choice. However, option flags can also be passed to functions that run doctests, establishing different defaults. In such cases, disabling an option via
-
in a directive can be useful.
doctest
is serious about requiring exact matches in expected output. If even a single character doesn’t match, the test fails. This will probably surprise you a few times, as you learn exactly what Python does and doesn’t guarantee about output. For example, when printing a dict, Python doesn’t guarantee that the key-value pairs will be printed in any particular order, so a test like
>>> foo()
{"Hermione": "hippogryph", "Harry": "broomstick"}
is vulnerable! One workaround is to do
>>> foo() == {"Hermione": "hippogryph", "Harry": "broomstick"}
True
instead. Another is to do
>>> d = sorted(foo().items())
>>> d
[('Harry', 'broomstick'), ('Hermione', 'hippogryph')]
There are others, but you get the idea.
Another bad idea is to print things that embed an object address, like
>>> id(1.0) # certain to fail some of the time
7948648
>>> class C: pass
>>> C() # the default repr() for instances embeds an address
<__main__.C instance at 0x00AC18F0>
ELLIPSIS
directive gives a nice approach for the last example:
>>> C()
<__main__.C instance at 0x...>
Floating-point numbers are also subject to small output variations across platforms, because Python defers to the platform C library for float formatting, and C libraries vary widely in quality here.
>>> 1./7 # risky
0.14285714285714285
>>> print(1./7) # safer
0.142857142857
>>> print(round(1./7, 6)) # much safer
0.142857
Numbers of the form
I/2.**J
are safe across all platforms, and I often contrive doctest examples to produce numbers of that form:
>>> 3./4 # utterly safe
0.75
Simple fractions are also easier for people to understand, and that makes for better documentation.
函数
testmod()
and
testfile()
provide a simple interface to doctest that should be sufficient for most basic uses. For a less formal introduction to these two functions, see sections
Simple Usage: Checking Examples in Docstrings
and
Simple Usage: Checking Examples in a Text File
.
doctest.
testfile
(
filename
,
module_relative=True
,
name=None
,
package=None
,
globs=None
,
verbose=None
,
report=True
,
optionflags=0
,
extraglobs=None
,
raise_on_error=False
,
parser=DocTestParser()
,
encoding=None
)
¶
All arguments except filename are optional, and should be specified in keyword form.
Test examples in the file named
filename
。返回
(failure_count,
test_count)
.
可选自变量 module_relative specifies how the filename should be interpreted:
True
(the default), then
filename
specifies an OS-independent module-relative path. By default, this path is relative to the calling module’s directory; but if the
package
argument is specified, then it is relative to that package. To ensure OS-independence,
filename
should use
/
characters to separate path segments, and may not be an absolute path (i.e., it may not begin with
/
).
False
, then
filename
specifies an OS-specific path. The path may be absolute or relative; relative paths are resolved with respect to the current working directory.
可选自变量
name
gives the name of the test; by default, or if
None
,
os.path.basename(filename)
被使用。
可选自变量
package
is a Python package or the name of a Python package whose directory should be used as the base directory for a module-relative filename. If no package is specified, then the calling module’s directory is used as the base directory for module-relative filenames. It is an error to specify
package
if
module_relative
is
False
.
可选自变量
globs
gives a dict to be used as the globals when executing examples. A new shallow copy of this dict is created for the doctest, so its examples start with a clean slate. By default, or if
None
, a new empty dict is used.
可选自变量
extraglobs
gives a dict merged into the globals used to execute examples. This works like
dict.update()
: if
globs
and
extraglobs
have a common key, the associated value in
extraglobs
appears in the combined dict. By default, or if
None
, no extra globals are used. This is an advanced feature that allows parameterization of doctests. For example, a doctest can be written for a base class, using a generic name for the class, then reused to test any number of subclasses by passing an
extraglobs
dict mapping the generic name to the subclass to be tested.
可选自变量
verbose
prints lots of stuff if true, and prints only failures if false; by default, or if
None
, it’s true if and only if
'-v'
是在
sys.argv
.
可选自变量 report prints a summary at the end when true, else prints nothing at the end. In verbose mode, the summary is detailed, else the summary is very brief (in fact, empty if all tests passed).
可选自变量 optionflags (default value 0) takes the bitwise OR of option flags. See section 选项标志 .
可选自变量 raise_on_error defaults to false. If true, an exception is raised upon the first failure or unexpected exception in an example. This allows failures to be post-mortem debugged. Default behavior is to continue running examples.
可选自变量
parser
specifies a
DocTestParser
(or subclass) that should be used to extract tests from the files. It defaults to a normal parser (i.e.,
DocTestParser()
).
可选自变量 encoding specifies an encoding that should be used to convert the file to unicode.
doctest.
testmod
(
m=None
,
name=None
,
globs=None
,
verbose=None
,
report=True
,
optionflags=0
,
extraglobs=None
,
raise_on_error=False
,
exclude_empty=False
)
¶
All arguments are optional, and all except for m should be specified in keyword form.
Test examples in docstrings in functions and classes reachable from module
m
(or module
__main__
if
m
is not supplied or is
None
), starting with
m.__doc__
.
Also test examples reachable from dict
m.__test__
, if it exists and is not
None
.
m.__test__
maps names (strings) to functions, classes and strings; function and class docstrings are searched for examples; strings are searched directly, as if they were docstrings.
Only docstrings attached to objects belonging to module m are searched.
返回
(failure_count,
test_count)
.
可选自变量
name
gives the name of the module; by default, or if
None
,
m.__name__
被使用。
可选自变量
exclude_empty
defaults to false. If true, objects for which no doctests are found are excluded from consideration. The default is a backward compatibility hack, so that code still using
doctest.master.summarize()
in conjunction with
testmod()
continues to get output for objects with no tests. The
exclude_empty
argument to the newer
DocTestFinder
constructor defaults to true.
Optional arguments
extraglobs
,
verbose
,
report
,
optionflags
,
raise_on_error
，和
globs
are the same as for function
testfile()
above, except that
globs
默认为
m.__dict__
.
doctest.
run_docstring_examples
(
f
,
globs
,
verbose=False
,
name="NoName"
,
compileflags=None
,
optionflags=0
)
¶
Test examples associated with object f ; for example, f may be a string, a module, a function, or a class object.
A shallow copy of dictionary argument globs is used for the execution context.
可选自变量
name
is used in failure messages, and defaults to
"NoName"
.
If optional argument verbose is true, output is generated even if there are no failures. By default, output is generated only in case of an example failure.
可选自变量
compileflags
gives the set of flags that should be used by the Python compiler when running the examples. By default, or if
None
, flags are deduced corresponding to the set of future features found in
globs
.
可选自变量
optionflags
works as for function
testfile()
above.
As your collection of doctest’ed modules grows, you’ll want a way to run all their doctests systematically.
doctest
provides two functions that can be used to create
unittest
test suites from modules and text files containing doctests. To integrate with
unittest
test discovery, include a
load_tests()
function in your test module:
import unittest
import doctest
import my_module_with_doctests
def load_tests(loader, tests, ignore):
tests.addTests(doctest.DocTestSuite(my_module_with_doctests))
return tests
There are two main functions for creating
unittest.TestSuite
instances from text files and modules with doctests:
doctest.
DocFileSuite
(
*paths
,
module_relative=True
,
package=None
,
setUp=None
,
tearDown=None
,
globs=None
,
optionflags=0
,
parser=DocTestParser()
,
encoding=None
)
¶
Convert doctest tests from one or more text files to a
unittest.TestSuite
.
返回的
unittest.TestSuite
is to be run by the unittest framework and runs the interactive examples in each file. If an example in any file fails, then the synthesized unit test fails, and a
failureException
exception is raised showing the name of the file containing the test and a (sometimes approximate) line number.
Pass one or more paths (as strings) to text files to be examined.
Options may be provided as keyword arguments:
可选自变量 module_relative specifies how the filenames in paths should be interpreted:
True
(the default), then each filename in
paths
specifies an OS-independent module-relative path. By default, this path is relative to the calling module’s directory; but if the
package
argument is specified, then it is relative to that package. To ensure OS-independence, each filename should use
/
characters to separate path segments, and may not be an absolute path (i.e., it may not begin with
/
).
False
, then each filename in
paths
specifies an OS-specific path. The path may be absolute or relative; relative paths are resolved with respect to the current working directory.
可选自变量
package
is a Python package or the name of a Python package whose directory should be used as the base directory for module-relative filenames in
paths
. If no package is specified, then the calling module’s directory is used as the base directory for module-relative filenames. It is an error to specify
package
if
module_relative
is
False
.
可选自变量
setUp
specifies a set-up function for the test suite. This is called before running the tests in each file. The
setUp
function will be passed a
DocTest
object. The setUp function can access the test globals as the
globs
attribute of the test passed.
可选自变量
tearDown
specifies a tear-down function for the test suite. This is called after running the tests in each file. The
tearDown
function will be passed a
DocTest
object. The setUp function can access the test globals as the
globs
attribute of the test passed.
可选自变量 globs is a dictionary containing the initial global variables for the tests. A new copy of this dictionary is created for each test. By default, globs is a new empty dictionary.
可选自变量
optionflags
specifies the default doctest options for the tests, created by or-ing together individual option flags. See section
选项标志
. See function
set_unittest_reportflags()
below for a better way to set reporting options.
可选自变量
parser
specifies a
DocTestParser
(or subclass) that should be used to extract tests from the files. It defaults to a normal parser (i.e.,
DocTestParser()
).
可选自变量 encoding specifies an encoding that should be used to convert the file to unicode.
全局
__file__
is added to the globals provided to doctests loaded from a text file using
DocFileSuite()
.
doctest.
DocTestSuite
(
module=None
,
globs=None
,
extraglobs=None
,
test_finder=None
,
setUp=None
,
tearDown=None
,
checker=None
)
¶
Convert doctest tests for a module to a
unittest.TestSuite
.
返回的
unittest.TestSuite
is to be run by the unittest framework and runs each doctest in the module. If any of the doctests fail, then the synthesized unit test fails, and a
failureException
exception is raised showing the name of the file containing the test and a (sometimes approximate) line number.
可选自变量 模块 provides the module to be tested. It can be a module object or a (possibly dotted) module name. If not specified, the module calling this function is used.
可选自变量 globs is a dictionary containing the initial global variables for the tests. A new copy of this dictionary is created for each test. By default, globs is a new empty dictionary.
可选自变量 extraglobs specifies an extra set of global variables, which is merged into globs . By default, no extra globals are used.
可选自变量
test_finder
是
DocTestFinder
object (or a drop-in replacement) that is used to extract doctests from the module.
Optional arguments
setUp
,
tearDown
，和
optionflags
are the same as for function
DocFileSuite()
above.
This function uses the same search technique as
testmod()
.
3.5 版改变：
DocTestSuite()
returns an empty
unittest.TestSuite
if
模块
contains no docstrings instead of raising
ValueError
.
Under the covers,
DocTestSuite()
创建
unittest.TestSuite
out of
doctest.DocTestCase
instances, and
DocTestCase
是子类对于
unittest.TestCase
.
DocTestCase
isn’t documented here (it’s an internal detail), but studying its code can answer questions about the exact details of
unittest
integration.
Similarly,
DocFileSuite()
创建
unittest.TestSuite
out of
doctest.DocFileCase
instances, and
DocFileCase
是子类对于
DocTestCase
.
So both ways of creating a
unittest.TestSuite
run instances of
DocTestCase
. This is important for a subtle reason: when you run
doctest
functions yourself, you can control the
doctest
options in use directly, by passing option flags to
doctest
functions. However, if you’re writing a
unittest
framework,
unittest
ultimately controls when and how tests get run. The framework author typically wants to control
doctest
reporting options (perhaps, e.g., specified by command line options), but there’s no way to pass options through
unittest
to
doctest
test runners.
For this reason,
doctest
also supports a notion of
doctest
reporting flags specific to
unittest
support, via this function:
doctest.
set_unittest_reportflags
(
flags
)
¶
设置
doctest
reporting flags to use.
Argument flags takes the bitwise OR of option flags. See section 选项标志 . Only “reporting flags” can be used.
This is a module-global setting, and affects all future doctests run by module
unittest
: the
runTest()
方法的
DocTestCase
looks at the option flags specified for the test case when the
DocTestCase
instance was constructed. If no reporting flags were specified (which is the typical and expected case),
doctest
’s
unittest
reporting flags are
bitwise ORed
into the option flags, and the option flags so augmented are passed to the
DocTestRunner
instance created to run the doctest. If any reporting flags were specified when the
DocTestCase
instance was constructed,
doctest
’s
unittest
reporting flags are ignored.
The value of the
unittest
reporting flags in effect before the function was called is returned by the function.
The basic API is a simple wrapper that’s intended to make doctest easy to use. It is fairly flexible, and should meet most users’ needs; however, if you require more fine-grained control over testing, or wish to extend doctest’s capabilities, then you should use the advanced API.
The advanced API revolves around two container classes, which are used to store the interactive examples extracted from doctest cases:
范例
: A single Python
语句
, paired with its expected output.
DocTest
: A collection of
范例
s, typically extracted from a single docstring or text file.
Additional processing classes are defined to find, parse, and run, and check doctest examples:
DocTestFinder
: Finds all docstrings in a given module, and uses a
DocTestParser
to create a
DocTest
from every docstring that contains interactive examples.
DocTestParser
: Creates a
DocTest
object from a string (such as an object’s docstring).
DocTestRunner
: Executes the examples in a
DocTest
, and uses an
OutputChecker
to verify their output.
OutputChecker
: Compares the actual output from a doctest example with the expected output, and decides whether they match.
The relationships among these processing classes are summarized in the following diagram:
list of:
+------+ +---------+
|module| --DocTestFinder-> | DocTest | --DocTestRunner-> results
+------+ | ^ +---------+ | ^ (printed)
| | | Example | | |
v | | ... | v |
DocTestParser | Example | OutputChecker
+---------+
doctest.
DocTest
(
examples
,
globs
,
name
,
filename
,
lineno
,
docstring
)
¶
A collection of doctest examples that should be run in a single namespace. The constructor arguments are used to initialize the attributes of the same names.
DocTest
defines the following attributes. They are initialized by the constructor, and should not be modified directly.
examples
¶
A list of
范例
objects encoding the individual interactive Python examples that should be run by this test.
globs
¶
The namespace (aka globals) that the examples should be run in. This is a dictionary mapping names to values. Any changes to the namespace made by the examples (such as binding new variables) will be reflected in
globs
after the test is run.
name
¶
A string name identifying the
DocTest
. Typically, this is the name of the object or file that the test was extracted from.
filename
¶
The name of the file that this
DocTest
was extracted from; or
None
if the filename is unknown, or if the
DocTest
was not extracted from a file.
lineno
¶
The line number within
filename
where this
DocTest
begins, or
None
if the line number is unavailable. This line number is zero-based with respect to the beginning of the file.
docstring
¶
The string that the test was extracted from, or
None
if the string is unavailable, or if the test was not extracted from a string.
doctest.
范例
(
source
,
want
,
exc_msg=None
,
lineno=0
,
indent=0
,
options=None
)
¶
A single interactive example, consisting of a Python statement and its expected output. The constructor arguments are used to initialize the attributes of the same names.
范例
defines the following attributes. They are initialized by the constructor, and should not be modified directly.
source
¶
A string containing the example’s source code. This source code consists of a single Python statement, and always ends with a newline; the constructor adds a newline when necessary.
want
¶
The expected output from running the example’s source code (either from stdout, or a traceback in case of exception).
want
ends with a newline unless no output is expected, in which case it’s an empty string. The constructor adds a newline when necessary.
exc_msg
¶
The exception message generated by the example, if the example is expected to generate an exception; or
None
if it is not expected to generate an exception. This exception message is compared against the return value of
traceback.format_exception_only()
.
exc_msg
ends with a newline unless it’s
None
. The constructor adds a newline if needed.
lineno
¶
The line number within the string containing this example where the example begins. This line number is zero-based with respect to the beginning of the containing string.
indent
¶
The example’s indentation in the containing string, i.e., the number of space characters that precede the example’s first prompt.
选项
¶
A dictionary mapping from option flags to
True
or
False
, which is used to override default options for this example. Any option flags not contained in this dictionary are left at their default value (as specified by the
DocTestRunner
’s
optionflags
). By default, no options are set.
doctest.
DocTestFinder
(
verbose=False
,
parser=DocTestParser()
,
recurse=True
,
exclude_empty=True
)
¶
A processing class used to extract the
DocTest
s that are relevant to a given object, from its docstring and the docstrings of its contained objects.
DocTest
s can be extracted from modules, classes, functions, methods, staticmethods, classmethods, and properties.
可选自变量
verbose
can be used to display the objects searched by the finder. It defaults to
False
(no output).
可选自变量
parser
specifies the
DocTestParser
object (or a drop-in replacement) that is used to extract doctests from docstrings.
If the optional argument
recurse
为 False，那么
DocTestFinder.find()
will only examine the given object, and not any contained objects.
If the optional argument
exclude_empty
为 False，那么
DocTestFinder.find()
will include tests for objects with empty docstrings.
DocTestFinder
defines the following method:
find
(
obj[, name][, module][, globs][, extraglobs]
)
¶
Return a list of the
DocTest
s that are defined by
obj
’s docstring, or by any of its contained objects’ docstrings.
可选自变量
name
specifies the object’s name; this name will be used to construct names for the returned
DocTest
s. If
name
is not specified, then
obj.__name__
被使用。
可选参数
模块
is the module that contains the given object. If the module is not specified or is
None
, then the test finder will attempt to automatically determine the correct module. The object’s module is used:
若
模块
is
False
, no attempt to find the module will be made. This is obscure, of use mostly in testing doctest itself: if
模块
is
False
, or is
None
but cannot be found automatically, then all objects are considered to belong to the (non-existent) module, so all contained objects will (recursively) be searched for doctests.
The globals for each
DocTest
is formed by combining
globs
and
extraglobs
(bindings in
extraglobs
override bindings in
globs
). A new shallow copy of the globals dictionary is created for each
DocTest
。若
globs
is not specified, then it defaults to the module’s
__dict__
, if specified, or
{}
otherwise. If
extraglobs
is not specified, then it defaults to
{}
.
doctest.
DocTestParser
¶
A processing class used to extract interactive examples from a string, and use them to create a
DocTest
对象。
DocTestParser
defines the following methods:
get_doctest
(
string
,
globs
,
name
,
filename
,
lineno
)
¶
Extract all doctest examples from the given string, and collect them into a
DocTest
对象。
globs
,
name
,
filename
，和
lineno
are attributes for the new
DocTest
object. See the documentation for
DocTest
了解更多信息。
doctest.
DocTestRunner
(
checker=None
,
verbose=None
,
optionflags=0
)
¶
A processing class used to execute and verify the interactive examples in a
DocTest
.
The comparison between expected outputs and actual outputs is done by an
OutputChecker
. This comparison may be customized with a number of option flags; see section
选项标志
for more information. If the option flags are insufficient, then the comparison may also be customized by passing a subclass of
OutputChecker
to the constructor.
The test runner’s display output can be controlled in two ways. First, an output function can be passed to
TestRunner.run()
; this function will be called with strings that should be displayed. It defaults to
sys.stdout.write
. If capturing the output is not sufficient, then the display output can be also customized by subclassing DocTestRunner, and overriding the methods
report_start()
,
report_success()
,
report_unexpected_exception()
，和
report_failure()
.
The optional keyword argument
checker
specifies the
OutputChecker
object (or drop-in replacement) that should be used to compare the expected outputs to the actual outputs of doctest examples.
The optional keyword argument
verbose
controls the
DocTestRunner
’s verbosity. If
verbose
is
True
, then information is printed about each example, as it is run. If
verbose
is
False
, then only failures are printed. If
verbose
is unspecified, or
None
, then verbose output is used iff the command-line switch
-v
被使用。
The optional keyword argument optionflags can be used to control how the test runner compares expected output to actual output, and how it displays failures. For more information, see section 选项标志 .
DocTestParser
defines the following methods:
report_start
(
out
,
test
,
example
)
¶
Report that the test runner is about to process the given example. This method is provided to allow subclasses of
DocTestRunner
to customize their output; it should not be called directly.
example
is the example about to be processed.
test
is the test
containing example
.
out
is the output function that was passed to
DocTestRunner.run()
.
report_success
(
out
,
test
,
example
,
got
)
¶
Report that the given example ran successfully. This method is provided to allow subclasses of
DocTestRunner
to customize their output; it should not be called directly.
example
is the example about to be processed.
got
is the actual output from the example.
test
is the test containing
example
.
out
is the output function that was passed to
DocTestRunner.run()
.
report_failure
(
out
,
test
,
example
,
got
)
¶
Report that the given example failed. This method is provided to allow subclasses of
DocTestRunner
to customize their output; it should not be called directly.
example
is the example about to be processed.
got
is the actual output from the example.
test
is the test containing
example
.
out
is the output function that was passed to
DocTestRunner.run()
.
report_unexpected_exception
(
out
,
test
,
example
,
exc_info
)
¶
Report that the given example raised an unexpected exception. This method is provided to allow subclasses of
DocTestRunner
to customize their output; it should not be called directly.
example
is the example about to be processed.
exc_info
is a tuple containing information about the unexpected exception (as returned by
sys.exc_info()
).
test
is the test containing
example
.
out
is the output function that was passed to
DocTestRunner.run()
.
run
(
test
,
compileflags=None
,
out=None
,
clear_globs=True
)
¶
Run the examples in
test
(a
DocTest
object), and display the results using the writer function
out
.
The examples are run in the namespace
test.globs
。若
clear_globs
is true (the default), then this namespace will be cleared after the test runs, to help with garbage collection. If you would like to examine the namespace after the test completes, then use
clear_globs=False
.
compileflags gives the set of flags that should be used by the Python compiler when running the examples. If not specified, then it will default to the set of future-import flags that apply to globs .
The output of each example is checked using the
DocTestRunner
’s output checker, and the results are formatted by the
DocTestRunner.report_*()
方法。
summarize
(
verbose=None
)
¶
Print a summary of all the test cases that have been run by this DocTestRunner, and return a
命名元组
TestResults(failed,
attempted)
.
可选
verbose
argument controls how detailed the summary is. If the verbosity is not specified, then the
DocTestRunner
’s verbosity is used.
doctest.
OutputChecker
¶
A class used to check the whether the actual output from a doctest example matches the expected output.
OutputChecker
defines two methods:
check_output()
, which compares a given pair of outputs, and returns true if they match; and
output_difference()
, which returns a string describing the differences between two outputs.
OutputChecker
defines the following methods:
check_output
(
want
,
got
,
optionflags
)
¶
返回
True
iff the actual output from an example (
got
) matches the expected output (
want
). These strings are always considered to match if they are identical; but depending on what option flags the test runner is using, several non-exact match types are also possible. See section
选项标志
for more information about option flags.
output_difference
(
example
,
got
,
optionflags
)
¶
Return a string describing the differences between the expected output for a given example ( example ) and the actual output ( got ). optionflags is the set of option flags used to compare want and got .
Doctest provides several mechanisms for debugging doctest examples:
Several functions convert doctests to executable Python programs, which can be run under the Python debugger,
pdb
.
DebugRunner
类是子类化的
DocTestRunner
that raises an exception for the first failing example, containing information about that example. This information can be used to perform post-mortem debugging on the example.
unittest
cases generated by
DocTestSuite()
support the
debug()
method defined by
unittest.TestCase
.
You can add a call to
pdb.set_trace()
in a doctest example, and you’ll drop into the Python debugger when that line is executed. Then you can inspect current values of variables, and so on. For example, suppose
a.py
contains just this module docstring:
"""
>>> def f(x):
... g(x*2)
>>> def g(x):
... print(x+3)
... import pdb; pdb.set_trace()
>>> f(3)
9
"""
Then an interactive Python session may look like this:
>>> import a, doctest
>>> doctest.testmod(a)
--Return--
> <doctest a[1]>(3)g()->None
-> import pdb; pdb.set_trace()
(Pdb) list
1 def g(x):
2 print(x+3)
3 -> import pdb; pdb.set_trace()
[EOF]
(Pdb) p x
6
(Pdb) step
--Return--
> <doctest a[0]>(2)f()->None
-> g(x*2)
(Pdb) list
1 def f(x):
2 -> g(x*2)
[EOF]
(Pdb) p x
3
(Pdb) step
--Return--
> <doctest a[2]>(1)?()->None
-> f(3)
(Pdb) cont
(0, 3)
>>>
Functions that convert doctests to Python code, and possibly run the synthesized code under the debugger:
doctest.
script_from_examples
(
s
)
¶
Convert text with examples to a script.
Argument s is a string containing doctest examples. The string is converted to a Python script, where doctest examples in s are converted to regular code, and everything else is converted to Python comments. The generated script is returned as a string. For example,
import doctest
print(doctest.script_from_examples(r"""
Set x and y to 1 and 2.
>>> x, y = 1, 2
Print their sum:
>>> print(x+y)
3
"""))
displays:
# Set x and y to 1 and 2.
x, y = 1, 2
#
# Print their sum:
print(x+y)
# Expected:
## 3
This function is used internally by other functions (see below), but can also be useful when you want to transform an interactive Python session into a Python script.
doctest.
testsource
(
模块
,
name
)
¶
Convert the doctest for an object to a script.
Argument
模块
is a module object, or dotted name of a module, containing the object whose doctests are of interest. Argument
name
is the name (within the module) of the object with the doctests of interest. The result is a string, containing the object’s docstring converted to a Python script, as described for
script_from_examples()
above. For example, if module
a.py
contains a top-level function
f()
, then
import a, doctest
print(doctest.testsource(a, "a.f"))
prints a script version of function
f()
’s docstring, with doctests converted to code, and the rest placed in comments.
doctest.
debug
(
模块
,
name
,
pm=False
)
¶
Debug the doctests for an object.
模块
and
name
arguments are the same as for function
testsource()
above. The synthesized Python script for the named object’s docstring is written to a temporary file, and then that file is run under the control of the Python debugger,
pdb
.
A shallow copy of
module.__dict__
is used for both local and global execution context.
可选自变量
pm
controls whether post-mortem debugging is used. If
pm
has a true value, the script file is run directly, and the debugger gets involved only if the script terminates via raising an unhandled exception. If it does, then post-mortem debugging is invoked, via
pdb.post_mortem()
, passing the traceback object from the unhandled exception. If
pm
is not specified, or is false, the script is run under the debugger from the start, via passing an appropriate
exec()
call to
pdb.run()
.
doctest.
debug_src
(
src
,
pm=False
,
globs=None
)
¶
Debug the doctests in a string.
This is like function
debug()
above, except that a string containing doctest examples is specified directly, via the
src
自变量。
可选自变量
pm
has the same meaning as in function
debug()
above.
可选自变量
globs
gives a dictionary to use as both local and global execution context. If not specified, or
None
, an empty dictionary is used. If specified, a shallow copy of the dictionary is used.
DebugRunner
class, and the special exceptions it may raise, are of most interest to testing framework authors, and will only be sketched here. See the source code, and especially
DebugRunner
’s docstring (which is a doctest!) for more details:
doctest.
DebugRunner
(
checker=None
,
verbose=None
,
optionflags=0
)
¶
子类化的
DocTestRunner
that raises an exception as soon as a failure is encountered. If an unexpected exception occurs, an
UnexpectedException
exception is raised, containing the test, the example, and the original exception. If the output doesn’t match, then a
DocTestFailure
exception is raised, containing the test, the example, and the actual output.
For information about the constructor parameters and methods, see the documentation for
DocTestRunner
in section
Advanced API
.
There are two exceptions that may be raised by
DebugRunner
实例：
doctest.
DocTestFailure
(
test
,
example
,
got
)
¶
An exception raised by
DocTestRunner
to signal that a doctest example’s actual output did not match its expected output. The constructor arguments are used to initialize the attributes of the same names.
DocTestFailure
defines the following attributes:
DocTestFailure.
got
¶
The example’s actual output.
doctest.
UnexpectedException
(
test
,
example
,
exc_info
)
¶
An exception raised by
DocTestRunner
to signal that a doctest example raised an unexpected exception. The constructor arguments are used to initialize the attributes of the same names.
UnexpectedException
defines the following attributes:
UnexpectedException.
exc_info
¶
A tuple containing information about the unexpected exception, as returned by
sys.exc_info()
.
As mentioned in the introduction,
doctest
has grown to have three primary uses:
These uses have different requirements, and it is important to distinguish them. In particular, filling your docstrings with obscure test cases makes for bad documentation.
When writing a docstring, choose docstring examples with care. There’s an art to this that needs to be learned—it may not be natural at first. Examples should add genuine value to the documentation. A good example can often be worth many words. If done with care, the examples will be invaluable for your users, and will pay back the time it takes to collect them many times over as the years go by and things change. I’m still amazed at how often one of my
doctest
examples stops working after a “harmless” change.
Doctest also makes an excellent tool for regression testing, especially if you don’t skimp on explanatory text. By interleaving prose and examples, it becomes much easier to keep track of what’s actually being tested, and why. When a test fails, good prose can make it much easier to figure out what the problem is, and how it should be fixed. It’s true that you could write extensive comments in code-based testing, but few programmers do. Many have found that using doctest approaches instead leads to much clearer tests. Perhaps this is simply because doctest makes writing prose a little easier than writing code, while writing comments in code is a little harder. I think it goes deeper than just that: the natural attitude when writing a doctest-based test is that you want to explain the fine points of your software, and illustrate them with examples. This in turn naturally leads to test files that start with the simplest features, and logically progress to complications and edge cases. A coherent narrative is the result, instead of a collection of isolated functions that test isolated bits of functionality seemingly at random. It’s a different attitude, and produces different results, blurring the distinction between testing and explaining.
Regression testing is best confined to dedicated objects or files. There are several options for organizing tests:
testfile()
or
DocFileSuite()
. This is recommended, although is easiest to do for new projects, designed from the start to use doctest.
_regrtest_topic
that consist of single docstrings, containing test cases for the named topics. These functions can be included in the same file as the module, or separated out into a separate test file.
__test__
dictionary mapping from regression test topics to docstrings containing test cases.
When you have placed your tests in a module, the module can itself be the test runner. When a test fails, you can arrange for your test runner to re-run only the failing doctest while you debug the problem. Here is a minimal example of such a test runner:
if __name__ == '__main__':
import doctest
flags = doctest.REPORT_NDIFF|doctest.FAIL_FAST
if len(sys.argv) > 1:
name = sys.argv[1]
if name in globals():
obj = globals()[name]
else:
obj = __test__[name]
doctest.run_docstring_examples(obj, globals(), name=name,
optionflags=flags)
else:
fail, total = doctest.testmod(optionflags=flags)
print("{} failures out of {} tests".format(fail, total))
脚注
| [1] | Examples containing both expected output and an exception are not supported. Trying to guess where one ends and the other begins is too error-prone, and that also makes for a confusing test. |