Code coverage for `bun test` (#3975)

* WIP code coverage initial commit

* almost works

* one approach

* Code Coverage

* Update WebKit

* it works but is not yet accurate

* skip double ascii check

* wrapper

* it works but i'm not sure what to do about blocks

* hide blocks for now

* Update ZigSourceProvider.cpp

* Create coverage.md

* Update nav.ts

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/docs/test/coverage.md b/docs/test/coverage.md
new file mode 100644
index 000000000..abf8cf94c
--- /dev/null
+++ b/docs/test/coverage.md
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+`bun:test` supports seeing which lines of code are covered by tests. To use this feature, pass `--coverage` to the CLI:
+
+```sh
+bun test --coverage
+```
+
+It will print out a coverage report to the console:
+
+```js
+-------------|---------|---------|-------------------
+File         | % Funcs | % Lines | Uncovered Line #s
+-------------|---------|---------|-------------------
+All files    |   38.89 |   42.11 |
+ index-0.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-1.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-10.ts |   33.33 |   36.84 | 10-15,19-24
+ index-2.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-3.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-4.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-5.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-6.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-7.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-8.ts  |   33.33 |   36.84 | 10-15,19-24
+ index-9.ts  |   33.33 |   36.84 | 10-15,19-24
+ index.ts    |  100.00 |  100.00 |
+-------------|---------|---------|-------------------
+```
+
+If coverage is below a threshold, `bun:test` will exit with a non-zero exit code to indicate the failure.
+
+### Configuring coverage
+
+`bunfig.toml` supports configuring coverage:
+
+```toml
+[test]
+
+# Always enable coverage
+coverage = true
+
+# Anything less than 90% coverage will fail the test
+# coverageThreshold = 0.9
+coverageThreshold = { line = 0.9, function = 0.9 }
+
+
+# Don't include .test.* files in coverage reports
+coverageSkipTestFiles = true
+
+# Disable sourcemap support in coverage reports
+# By default, coverage reports will automatically use Bun's internal sourcemap.
+# You probably don't want to configure this
+# coverageIgnoreSourcemaps = false
+```
+
+`coverageThreshold` can be either a number or an object with `line` and `function` keys. When a number, it is treated as both the line and function threshold.
+
+Coverage support was added in Bun v0.7.2.