# Kotlin test coverage

> Set up Supercov with your agent, or run it yourself with Gradle.

Web page: https://supercov.com/docs/kotlin
All Supercov pages for agents: https://supercov.com/llms.txt · Full text: https://supercov.com/llms-full.txt

Ask your coding agent to set up Supercov in your project:

```text supercov-prompt
Install Supercov with brew install supercorp-ai/tap/supercov, or take the
platform archive from the GitHub release. Read supercov docs and check the
supported JDK before running our existing Gradle tests. Show the coverage
report and any measurement limits. Don't change application code or tests.
```

## Run it yourself

Kotlin support requires a JDK 17 or newer with Gradle or Maven. Kotlin has no
package registry of its own here, so the project takes the binary directly:

```sh
brew install supercorp-ai/tap/supercov
supercov --version
```

`npx supercov` works where Node.js is already present, and the platform
archives on the [latest release](https://github.com/supercorp-ai/supercov/releases/latest)
carry the same build at the same version.

### Run your tests

From your project root:

```sh
supercov -- ./gradlew test
```

Keep the flags your build normally uses. Supercov drives Gradle as your test
command rather than as a plugin: it adds the JUnit Platform launcher it needs
to the build file inside its own isolated workspace copy, so your
`build.gradle.kts` is never edited.

Kotest and Spock run on the JUnit Platform, so Supercov measures them the same
way it measures JUnit 5 and TestNG.

Inspect the run:

```sh
supercov runs latest
supercov runs latest gaps --limit 5
```

## Check what the tests assert

Line coverage tells you a statement ran. It does not tell you that a test
checked the result. Supercov can ask [Jev](https://typesafe.ai) whether each test would fail if a
statement it ran changed. `runs latest assertions assess` saves the answers
(it needs `TYPESAFE_API_KEY`), and `runs latest assertions` then lists the
statements no test checks, file by file. A statement that is not asserted
runs in some test, but nothing that test checks depends on it. See
[Assertion coverage](https://supercov.com/docs/assertions?language=kotlin).

## Kotlin-specific limits

Supercov measures the classes your build compiles for the test run. Inline
functions and generated sources have measurement limits of their own. See
[runner support](https://supercov.com/docs/supported-suites?language=kotlin#java-and-kotlin) for the detail
available from each engine.

Already using Kover or JaCoCo? See [how the reports differ](https://supercov.com/compare/kotlin-code-coverage.md).
`supercov docs coverage-model` prints the guide for your installed version.