Test runner

自 v16.17.0 版本开始新增

源代码： lib/test.js

The node:test module facilitates the creation of JavaScript tests that report results in TAP format. To access it:

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This module is only available under the node: scheme. The following will not work:

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Tests created via the test module consist of a single function that is processed in one of three ways:

1. A synchronous function that is considered failing if it throws an exception, and is considered passing otherwise.
2. A function that returns a Promise that is considered failing if the Promise rejects, and is considered passing if the Promise resolves.
3. A function that receives a callback function. If the callback receives any truthy value as its first argument, the test is considered failing. If a falsy value is passed as the first argument to the callback, the test is considered passing. If the test function receives a callback function and also returns a Promise, the test will fail.

The following example illustrates how tests are written using the test module.

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As a test file executes, TAP is written to the standard output of the Node.js process. This output can be interpreted by any test harness that understands the TAP format. If any tests fail, the process exit code is set to 1.

Subtests

The test context's test() method allows subtests to be created. This method behaves identically to the top level test() function. The following example demonstrates the creation of a top level test with two subtests.

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In this example, await is used to ensure that both subtests have completed. This is necessary because parent tests do not wait for their subtests to complete. Any subtests that are still outstanding when their parent finishes are cancelled and treated as failures. Any subtest failures cause the parent test to fail.

Skipping tests

Individual tests can be skipped by passing the skip option to the test, or by calling the test context's skip() method. Both of these options support including a message that is displayed in the TAP output as shown in the following example.

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M describe/it syntax

Running tests can also be done using describe to declare a suite and it to declare a test. A suite is used to organize and group related tests together. it is an alias for test, except there is no test context passed, since nesting is done using suites.

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describe and it are imported from the node:test module.

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M only tests

If Node.js is started with the --test-only command-line option, it is possible to skip all top level tests except for a selected subset by passing the only option to the tests that should be run. When a test with the only option set is run, all subtests are also run. The test context's runOnly() method can be used to implement the same behavior at the subtest level.

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Extraneous asynchronous activity

Once a test function finishes executing, the TAP results are output as quickly as possible while maintaining the order of the tests. However, it is possible for the test function to generate asynchronous activity that outlives the test itself. The test runner handles this type of activity, but does not delay the reporting of test results in order to accommodate it.

In the following example, a test completes with two setImmediate() operations still outstanding. The first setImmediate() attempts to create a new subtest. Because the parent test has already finished and output its results, the new subtest is immediately marked as failed, and reported in the top level of the file's TAP output.

The second setImmediate() creates an uncaughtException event. uncaughtException and unhandledRejection events originating from a completed test are handled by the test module and reported as diagnostic warnings in the top level of the file's TAP output.

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Running tests from the command line

The Node.js test runner can be invoked from the command line by passing the --test flag:

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By default, Node.js will recursively search the current directory for JavaScript source files matching a specific naming convention. Matching files are executed as test files. More information on the expected test file naming convention and behavior can be found in the test runner execution model section.

Alternatively, one or more paths can be provided as the final argument(s) to the Node.js command, as shown below.

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In this example, the test runner will execute the files test1.js and test2.mjs. The test runner will also recursively search the custom_test_dir/ directory for test files to execute.

Test runner execution model

When searching for test files to execute, the test runner behaves as follows:

• Any files explicitly provided by the user are executed.
• If the user did not explicitly specify any paths, the current working directory is recursively searched for files as specified in the following steps.
• node_modules directories are skipped unless explicitly provided by the user.
• If a directory named test is encountered, the test runner will search it recursively for all all .js, .cjs, and .mjs files. All of these files are treated as test files, and do not need to match the specific naming convention detailed below. This is to accommodate projects that place all of their tests in a single test directory.
• In all other directories, .js, .cjs, and .mjs files matching the following patterns are treated as test files:
  • ^test$ - Files whose basename is the string 'test'. Examples: test.js, test.cjs, test.mjs.
  • ^test-.+ - Files whose basename starts with the string 'test-' followed by one or more characters. Examples: test-example.js, test-another-example.mjs.
  • .+[\.\-\_]test$ - Files whose basename ends with .test, -test, or _test, preceded by one or more characters. Examples: example.test.js, example-test.cjs, example_test.mjs.
  • Other file types understood by Node.js such as .node and .json are not automatically executed by the test runner, but are supported if explicitly provided on the command line.

Each matching test file is executed in a separate child process. If the child process finishes with an exit code of 0, the test is considered passing. Otherwise, the test is considered to be a failure. Test files must be executable by Node.js, but are not required to use the node:test module internally.

M test([name][, options][, fn])

• name string The name of the test, which is displayed when reporting test results. Default: The name property of fn, or '<anonymous>' if fn does not have a name.
• options Object Configuration options for the test. The following properties are supported:
  • concurrency number | boolean If a number is provided, then that many tests would run in parallel. If truthy, it would run (number of cpu cores - 1) tests in parallel. For subtests, it will be Infinity tests in parallel. If falsy, it would only run one test at a time. If unspecified, subtests inherit this value from their parent. Default: false.
  • only boolean If truthy, and the test context is configured to run only tests, then this test will be run. Otherwise, the test is skipped. Default: false.
  • signal AbortSignal Allows aborting an in-progress test.
  • skip boolean | string If truthy, the test is skipped. If a string is provided, that string is displayed in the test results as the reason for skipping the test. Default: false.
  • todo boolean | string If truthy, the test marked as TODO. If a string is provided, that string is displayed in the test results as the reason why the test is TODO. Default: false.
  • timeout number A number of milliseconds the test will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.
• fn Function | AsyncFunction The function under test. The first argument to this function is a TestContext object. If the test uses callbacks, the callback function is passed as the second argument. Default: A no-op function.
• Returns: Promise Resolved with undefined once the test completes.

The test() function is the value imported from the test module. Each invocation of this function results in the creation of a test point in the TAP output.

The TestContext object passed to the fn argument can be used to perform actions related to the current test. Examples include skipping the test, adding additional TAP diagnostic information, or creating subtests.

test() returns a Promise that resolves once the test completes. The return value can usually be discarded for top level tests. However, the return value from subtests should be used to prevent the parent test from finishing first and cancelling the subtest as shown in the following example.

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The timeout option can be used to fail the test if it takes longer than timeout milliseconds to complete. However, it is not a reliable mechanism for canceling tests because a running test might block the application thread and thus prevent the scheduled cancellation.

M describe([name][, options][, fn])

• name string The name of the suite, which is displayed when reporting test results. Default: The name property of fn, or '<anonymous>' if fn does not have a name.
• options Object Configuration options for the suite. supports the same options as test([name][, options][, fn]).
• fn Function | AsyncFunction The function under suite declaring all subtests and subsuites. The first argument to this function is a SuiteContext object. Default: A no-op function.
• Returns: undefined.

The describe() function imported from the node:test module. Each invocation of this function results in the creation of a Subtest and a test point in the TAP output. After invocation of top level describe functions, all top level tests and suites will execute.

M describe.skip([name][, options][, fn])

Shorthand for skipping a suite, same as describe([name], { skip: true }[, fn]).

M describe.todo([name][, options][, fn])

Shorthand for marking a suite as TODO, same as describe([name], { todo: true }[, fn]).

M it([name][, options][, fn])

• name string The name of the test, which is displayed when reporting test results. Default: The name property of fn, or '<anonymous>' if fn does not have a name.
• options Object Configuration options for the suite. supports the same options as test([name][, options][, fn]).
• fn Function | AsyncFunction The function under test. If the test uses callbacks, the callback function is passed as an argument. Default: A no-op function.
• Returns: undefined.

The it() function is the value imported from the node:test module. Each invocation of this function results in the creation of a test point in the TAP output.

M it.skip([name][, options][, fn])

Shorthand for skipping a test, same as it([name], { skip: true }[, fn]).

M it.todo([name][, options][, fn])

Shorthand for marking a test as TODO, same as it([name], { todo: true }[, fn]).

M before([, fn][, options])

自 v16.18.0 版本开始新增

• fn Function | AsyncFunction The hook function. If the hook uses callbacks, the callback function is passed as the second argument. Default: A no-op function.
• options Object Configuration options for the hook. The following properties are supported:
  • signal AbortSignal Allows aborting an in-progress hook.
  • timeout number A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.

This function is used to create a hook running before running a suite.

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M after([, fn][, options])

自 v16.18.0 版本开始新增

• fn Function | AsyncFunction The hook function. If the hook uses callbacks, the callback function is passed as the second argument. Default: A no-op function.
• options Object Configuration options for the hook. The following properties are supported:
  • signal AbortSignal Allows aborting an in-progress hook.
  • timeout number A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.

This function is used to create a hook running after running a suite.

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M beforeEach([, fn][, options])

自 v16.18.0 版本开始新增

• fn Function | AsyncFunction The hook function. If the hook uses callbacks, the callback function is passed as the second argument. Default: A no-op function.
• options Object Configuration options for the hook. The following properties are supported:
  • signal AbortSignal Allows aborting an in-progress hook.
  • timeout number A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.

This function is used to create a hook running before each subtest of the current suite.

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M afterEach([, fn][, options])

自 v16.18.0 版本开始新增

• fn Function | AsyncFunction The hook function. If the hook uses callbacks, the callback function is passed as the second argument. Default: A no-op function.
• options Object Configuration options for the hook. The following properties are supported:
  • signal AbortSignal Allows aborting an in-progress hook.
  • timeout number A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.

This function is used to create a hook running after each subtest of the current test.

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C TestContext

自 v16.17.0 版本开始新增

An instance of TestContext is passed to each test function in order to interact with the test runner. However, the TestContext constructor is not exposed as part of the API.

M context.beforeEach([, fn][, options])

自 v16.18.0 版本开始新增

• fn Function | AsyncFunction The hook function. The first argument to this function is a TestContext object. If the hook uses callbacks, the callback function is passed as the second argument. Default: A no-op function.
• options Object Configuration options for the hook. The following properties are supported:
  • signal AbortSignal Allows aborting an in-progress hook.
  • timeout number A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.

This function is used to create a hook running before each subtest of the current test.

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M context.afterEach([, fn][, options])

自 v16.18.0 版本开始新增

• fn Function | AsyncFunction The hook function. The first argument to this function is a TestContext object. If the hook uses callbacks, the callback function is passed as the second argument. Default: A no-op function.
• options Object Configuration options for the hook. The following properties are supported:
  • signal AbortSignal Allows aborting an in-progress hook.
  • timeout number A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.

This function is used to create a hook running after each subtest of the current test.

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M context.diagnostic(message)

自 v16.17.0 版本开始新增

• message string Message to be displayed as a TAP diagnostic.

This function is used to write TAP diagnostics to the output. Any diagnostic information is included at the end of the test's results. This function does not return a value.

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M context.name

自 v16.18.0 版本开始新增

The name of the test.

M context.runOnly(shouldRunOnlyTests)

自 v16.17.0 版本开始新增

• shouldRunOnlyTests boolean Whether or not to run only tests.

If shouldRunOnlyTests is truthy, the test context will only run tests that have the only option set. Otherwise, all tests are run. If Node.js was not started with the --test-only command-line option, this function is a no-op.

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M context.signal

自 v16.17.0 版本开始新增

• AbortSignal Can be used to abort test subtasks when the test has been aborted.

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M context.skip([message])

自 v16.17.0 版本开始新增

• message string Optional skip message to be displayed in TAP output.

This function causes the test's output to indicate the test as skipped. If message is provided, it is included in the TAP output. Calling skip() does not terminate execution of the test function. This function does not return a value.

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M context.todo([message])

自 v16.17.0 版本开始新增

• message string Optional TODO message to be displayed in TAP output.

This function adds a TODO directive to the test's output. If message is provided, it is included in the TAP output. Calling todo() does not terminate execution of the test function. This function does not return a value.

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M context.test([name][, options][, fn])

• name string The name of the subtest, which is displayed when reporting test results. Default: The name property of fn, or '<anonymous>' if fn does not have a name.
• options Object Configuration options for the subtest. The following properties are supported:
  • concurrency number The number of tests that can be run at the same time. If unspecified, subtests inherit this value from their parent. Default: 1.
  • only boolean If truthy, and the test context is configured to run only tests, then this test will be run. Otherwise, the test is skipped. Default: false.
  • signal AbortSignal Allows aborting an in-progress test.
  • skip boolean | string If truthy, the test is skipped. If a string is provided, that string is displayed in the test results as the reason for skipping the test. Default: false.
  • todo boolean | string If truthy, the test marked as TODO. If a string is provided, that string is displayed in the test results as the reason why the test is TODO. Default: false.
  • timeout number A number of milliseconds the test will fail after. If unspecified, subtests inherit this value from their parent. Default: Infinity.
• fn Function | AsyncFunction The function under test. The first argument to this function is a TestContext object. If the test uses callbacks, the callback function is passed as the second argument. Default: A no-op function.
• Returns: Promise Resolved with undefined once the test completes.

This function is used to create subtests under the current test. This function behaves in the same fashion as the top level test() function.

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C SuiteContext

自 v16.17.0 版本开始新增

An instance of SuiteContext is passed to each suite function in order to interact with the test runner. However, the SuiteContext constructor is not exposed as part of the API.

M context.name

自 v16.18.0 版本开始新增

The name of the suite.

M context.signal

自 v16.17.0 版本开始新增

• AbortSignal Can be used to abort test subtasks when the test has been aborted.