1# Chroma lexers
2
3All lexers in Chroma should now be defined in XML unless they require custom code.
4
5## Lexer tests
6
7The tests in this directory feed a known input `testdata/<name>.actual` into the parser for `<name>` and check
8that its output matches `<name>.expected`.
9
10It is also possible to perform several tests on a same parser `<name>`, by placing know inputs `*.actual` into a
11directory `testdata/<name>/`.
12
13### Running the tests
14
15Run the tests as normal:
16```go
17go test ./lexers
18```
19
20### Update existing tests
21
22When you add a new test data file (`*.actual`), you need to regenerate all tests. That's how Chroma creates the `*.expected` test file based on the corresponding lexer.
23
24To regenerate all tests, type in your terminal:
25
26```go
27RECORD=true go test ./lexers
28```
29
30This first sets the `RECORD` environment variable to `true`. Then it runs `go test` on the `./lexers` directory of the Chroma project.
31
32(That environment variable tells Chroma it needs to output test data. After running `go test ./lexers` you can remove or reset that variable.)
33
34#### Windows users
35
36Windows users will find that the `RECORD=true go test ./lexers` command fails in both the standard command prompt terminal and in PowerShell.
37
38Instead we have to perform both steps separately:
39
40- Set the `RECORD` environment variable to `true`.
41 + In the regular command prompt window, the `set` command sets an environment variable for the current session: `set RECORD=true`. See [this page](https://superuser.com/questions/212150/how-to-set-env-variable-in-windows-cmd-line) for more.
42 + In PowerShell, you can use the `$env:RECORD = 'true'` command for that. See [this article](https://mcpmag.com/articles/2019/03/28/environment-variables-in-powershell.aspx) for more.
43 + You can also make a persistent environment variable by hand in the Windows computer settings. See [this article](https://www.computerhope.com/issues/ch000549.htm) for how.
44- When the environment variable is set, run `go test ./lexers`.
45
46Chroma will now regenerate the test files and print its results to the console window.
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