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275 lines
7.3 KiB
Markdown
275 lines
7.3 KiB
Markdown
# Testing
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Deno has a built-in test runner that you can use for testing JavaScript or
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TypeScript code.
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`deno test` will search in `./*` and `./**/*` recursively, for test files:
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- named `test.{ts, tsx, js, mjs, jsx}`,
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- or ending with `.test.{ts, tsx, js, mjs, jsx}`,
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- or ending with `_test.{ts, tsx, js, mjs, jsx}`
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## Writing tests
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To define a test you need to call `Deno.test` with a name and function to be
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tested. There are two styles you can use.
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```ts
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import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts";
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// Simple name and function, compact form, but not configurable
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Deno.test("hello world #1", () => {
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const x = 1 + 2;
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assertEquals(x, 3);
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});
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// Fully fledged test definition, longer form, but configurable (see below)
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Deno.test({
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name: "hello world #2",
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fn: () => {
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const x = 1 + 2;
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assertEquals(x, 3);
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},
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});
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```
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## Assertions
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There are some useful assertion utilities at
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https://deno.land/std@$STD_VERSION/testing#usage to make testing easier:
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```ts
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import {
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assertArrayIncludes,
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assertEquals,
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} from "https://deno.land/std@$STD_VERSION/testing/asserts.ts";
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Deno.test("hello world", () => {
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const x = 1 + 2;
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assertEquals(x, 3);
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assertArrayIncludes([1, 2, 3, 4, 5, 6], [3], "Expected 3 to be in the array");
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});
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```
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### Async functions
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You can also test asynchronous code by passing a test function that returns a
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promise. For this you can use the `async` keyword when defining a function:
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```ts
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import { delay } from "https://deno.land/std@$STD_VERSION/async/delay.ts";
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Deno.test("async hello world", async () => {
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const x = 1 + 2;
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// await some async task
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await delay(100);
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if (x !== 3) {
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throw Error("x should be equal to 3");
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}
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});
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```
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### Resource and async op sanitizers
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Certain actions in Deno create resources in the resource table
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([learn more here](./contributing/architecture.md)). These resources should be
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closed after you are done using them.
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For each test definition, the test runner checks that all resources created in
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this test have been closed. This is to prevent resource 'leaks'. This is enabled
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by default for all tests, but can be disabled by setting the `sanitizeResources`
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boolean to false in the test definition.
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The same is true for async operation like interacting with the filesystem. The
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test runner checks that each operation you start in the test is completed before
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the end of the test. This is enabled by default for all tests, but can be
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disabled by setting the `sanitizeOps` boolean to false in the test definition.
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```ts
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Deno.test({
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name: "leaky test",
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fn() {
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Deno.open("hello.txt");
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},
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sanitizeResources: false,
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sanitizeOps: false,
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});
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```
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### Exit sanitizer
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There's also the exit sanitizer which ensures that tested code doesn't call
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Deno.exit() signaling a false test success.
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This is enabled by default for all tests, but can be disabled by setting the
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`sanitizeExit` boolean to false in thetest definition.
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```ts
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Deno.test({
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name: "false success",
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fn() {
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Deno.exit(0);
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},
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sanitizeExit: false,
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});
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Deno.test({
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name: "failing test",
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fn() {
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throw new Error("this test fails");
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},
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});
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```
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## Running tests
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To run the test, call `deno test` with the file that contains your test
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function. You can also omit the file name, in which case all tests in the
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current directory (recursively) that match the glob
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`{*_,*.,}test.{js,mjs,ts,jsx,tsx}` will be run. If you pass a directory, all
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files in the directory that match this glob will be run.
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```shell
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# Run all tests in the current directory and all sub-directories
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deno test
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# Run all tests in the util directory
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deno test util/
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# Run just my_test.ts
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deno test my_test.ts
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```
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`deno test` uses the same permission model as `deno run` and therefore will
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require, for example, `--allow-write` to write to the file system during
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testing.
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To see all runtime options with `deno test`, you can reference the command line
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help:
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```shell
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deno help test
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```
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## Filtering
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There are a number of options to filter the tests you are running.
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### Command line filtering
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Tests can be run individually or in groups using the command line `--filter`
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option.
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The filter flags accept a string or a pattern as value.
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Assuming the following tests:
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```ts
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Deno.test({ name: "my-test", fn: myTest });
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Deno.test({ name: "test-1", fn: test1 });
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Deno.test({ name: "test2", fn: test2 });
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```
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This command will run all of these tests because they all contain the word
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"test".
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```shell
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deno test --filter "test" tests/
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```
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On the flip side, the following command uses a pattern and will run the second
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and third tests.
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```shell
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deno test --filter "/test-*\d/" tests/
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```
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_To let Deno know that you want to use a pattern, wrap your filter with
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forward-slashes like the JavaScript syntactic sugar for a REGEX._
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### Test definition filtering
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Within the tests themselves, you have two options for filtering.
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#### Filtering out (Ignoring these tests)
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Sometimes you want to ignore tests based on some sort of condition (for example
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you only want a test to run on Windows). For this you can use the `ignore`
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boolean in the test definition. If it is set to true the test will be skipped.
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```ts
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Deno.test({
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name: "do macOS feature",
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ignore: Deno.build.os !== "darwin",
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fn() {
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doMacOSFeature();
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},
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});
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```
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#### Filtering in (Only run these tests)
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Sometimes you may be in the middle of a problem within a large test class and
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you would like to focus on just that test and ignore the rest for now. For this
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you can use the `only` option to tell the test framework to only run tests with
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this set to true. Multiple tests can set this option. While the test run will
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report on the success or failure of each test, the overall test run will always
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fail if any test is flagged with `only`, as this is a temporary measure only
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which disables nearly all of your tests.
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```ts
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Deno.test({
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name: "Focus on this test only",
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only: true,
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fn() {
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testComplicatedStuff();
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},
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});
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```
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## Failing fast
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If you have a long running test suite and wish for it to stop on the first
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failure, you can specify the `--fail-fast` flag when running the suite.
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```shell
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deno test --fail-fast
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```
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## Test coverage
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Deno will collect test coverage into a directory for your code if you specify
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the `--coverage` flag when starting `deno test`.
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This coverage information is acquired directly from the JavaScript engine (V8)
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which is very accurate.
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This can then be further processed from the internal format into well known
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formats by the `deno coverage` tool.
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```
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# Go into your project's working directory
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git clone https://github.com/oakserver/oak && cd oak
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# Collect your coverage profile with deno test --coverage=<output_directory>
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deno test --coverage=cov_profile
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# From this you can get a pretty printed diff of uncovered lines
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deno coverage cov_profile
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# Or generate an lcov report
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deno coverage cov_profile --lcov > cov_profile.lcov
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# Which can then be further processed by tools like genhtml
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genhtml -o cov_profile/html cov_profile.lcov
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```
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By default, `deno coverage` will exclude any files matching the regular
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expression `test\.(js|mjs|ts|jsx|tsx)` and only consider including files
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matching the regular expression `^file:`.
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These filters can be overridden using the `--exclude` and `--include` flags. A
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source file's url must match both regular expressions for it to be a part of the
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report.
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