angular-docs-cn/aio/content/guide/testing-pipes.md
George Kalpakas 9021d3f5e1 docs: fix live examples in testing guides (#38038)
In #37957, parts of the testing guide were broken out into separate
guides. As part of that work, the `<live-example>` tags were also copied
to the new guides. These `<live-example>` tags did not specify the
targeted example project via the `name` attribute, thus they were
implicitly targeting the example with the same name as the guide they
were in. See the [Docs style guide][1] for more info.

However, there is only one example project (`testing/`) and all
`<live-example>` tags were supposed to target that. This worked fine on
the `testing.md` guide, but it broke on other guides (which tried to
target non-existing example projects based on their names).

This commit fixes it by explicitly specifying which example is targeted
by the `<live-example>` tags. It also removes the `embedded-style`
attribute that has no effect.

[1]: https://angular.io/guide/docs-style-guide#live-examples

Fixes #38036

PR Close #38038
2020-07-14 09:10:00 -07:00

1.6 KiB

Testing Pipes

You can test pipes without the Angular testing utilities.

For the sample app that the testing guides describe, see the sample app.

For the tests features in the testing guides, see tests.

Testing the TitleCasePipe

A pipe class has one method, transform, that manipulates the input value into a transformed output value. The transform implementation rarely interacts with the DOM. Most pipes have no dependence on Angular other than the @Pipe metadata and an interface.

Consider a TitleCasePipe that capitalizes the first letter of each word. Here's an implementation with a regular expression.

Anything that uses a regular expression is worth testing thoroughly. Use simple Jasmine to explore the expected cases and the edge cases.

{@a write-tests}

Writing DOM tests to support a pipe test

These are tests of the pipe in isolation. They can't tell if the TitleCasePipe is working properly as applied in the application components.

Consider adding component tests such as this one: