Project Level Config

Kotest is flexible and has many ways to configure tests, such as configuring the order of tests inside a spec, or how test classes are created. Sometimes you may want to set this at a global level and for that you need to use project-level-config.

Project level configuration can be used by creating a class that extends from AbstractProjectConfig. Note: On the JVM and JS platforms, an object is also supported if you prefer to a class.

Any configuration set at the Spec level or directly on a test will override the config specified at the project level.

Some configuration options available in KotestProjectConfig include parallelism of tests, failing specs with ignored tests, global AssertSoftly, and reusable listeners or extensions.

Runtime Detection

At runtime, Kotest will scan for classes that extend AbstractProjectConfig and instantiate them, using any configuration values defined in those classes.

You can create more than one config class in different modules, and any on the current classpath will be detected and configs merged. This is effective for allowing common config to be placed into a root module. In the case of clashes, one value will be arbitrarily picked, so it is not recommended adding competing settings to different configs.

If you have a large project, then you may wish to disable the auto scanning for these config classes if it is incurring a significant startup cost. You can do this by setting a system property or environment variable kotest.framework.classpath.scanning.config.disable to true.

Once auto scanning is disabled, if you wish to still use project config, you can specify a well known class name which Kotest will reflectively instantiate. The system property or environment variable to use is kotest.framework.config.fqn.

For example, setting:

kotest.framework.classpath.scanning.config.disable=true
kotest.framework.config.fqn=com.wibble.KotestConfig

Will disable runtime scanning, and look for a class com.wibble.KotestConfig. The class must still inherit AbstractProjectConfig.

tip

Another related setting is kotest.framework.classpath.scanning.autoscan.disable which can also be set to false for speed. With auto scan disabled, Kotest will not scan the classpath looking for for @AutoScan annotated extensions.

caution

System properties set in your gradle file won't be picked up by the intellij plugin if you have that installed. Instead, look to specify the properties inside a kotest.properties file. Full details here.

Parallelism

You can ask Kotest to run specs in parallel to take advantage of modern cpus with several cores by setting the parallelism level (default is 1). Tests inside a spec are always executed sequentially.

To do this, override parallelism inside your config and set it to a value higher than 1. The number set is the number of concurrently executing specs. For example.

object KotestProjectConfig : AbstractProjectConfig() {
    override val parallelism = 3
}

An alternative way to enable this is the system property kotest.framework.parallelism which will always (if defined) take priority over the value here.

Some tests may not play nice in parallel, so you can opt out individual specs and force them to be executed in isolation by using the @DoNotParallelize annotation on the spec.

note

This is only available on the JVM target.

Assertion Mode

You can ask Kotest to fail the build, or warn in std err, if a test is executed that does not use a Kotest assertion.

To do this, set assertionMode to AssertionMode.Error or AssertionMode.Warn inside your config. For example. An alternative way to enable this is the system property kotest.framework.assertion.mode which will always (if defined) take priority over the value here.

object KotestProjectConfig : AbstractProjectConfig() {
    override val assertionMode = AssertionMode.Error
}

caution

Assertion mode only works for Kotest assertions and not other assertion libraries. This is because the assertions need to opt-in to the assertion mode when enabled.

Global Assert Softly

Assert softly is very useful to batch up errors into a single failure. If we want to enable this for every test automatically, we can do this in a config. An alternative way to enable this is by setting system property kotest.framework.assertion.globalassertsoftly to true which will always (if defined) take priority over the value here.

object KotestProjectConfig : AbstractProjectConfig() {
    override val globalAssertSoftly = true
}

Duplicate Test Name Handling

By default, Kotest will rename a test if it has the same name as another test in the same scope. It will append _1, _2 and so on to the test name. This is useful for automatically generated tests.

You can change this behavior globally by setting duplicateTestNameMode to either DuplicateTestNameMode.Error or DuplicateTestNameMode.Warn.

Error will fail the test suite on a repeated name, and warn will rename but output a warning.

Fail On Ignored Tests

You may wish to consider an ignored test as a failure. To enable this feature, set failOnIgnoredTests to true inside your project config. For example.

object KotestProjectConfig : AbstractProjectConfig() {
    override val failOnIgnoredTests = true
}

Ordering

Kotest supports ordering both specs and tests independently.

Test Ordering

When running multiple tests from a Spec, there's a certain order on how to execute them.

By default, a sequential order is used (the order that tests are defined in the spec), but this can be changed. For available options see test ordering.

Spec Ordering

By default, the ordering of Spec classes is not defined. This is often sufficient, when we have no preference, but if we need control over the execution order of specs, we can use spec ordering.

Test Naming

Test names can be adjusted in several ways.

Test Case

Test names case can be controlled by changing the value of testNameCase.

By default, the value is TestNameCase.AsIs which makes no change.

By setting the value to TestNameCase.Lowercase a test's name will be lowercase in output.

If you are using a spec that adds in prefixes to the test names (should as WordSpec or BehaviorSpec) then the values TestNameCase.Sentence and TestNameCase.InitialLowercase can be useful.

Test Name Tags

Another using test name option is testNameAppendTags which, when set to true, will include any applicable tags in the test name. For example, if a test foo was defined in a spec with the tags linux and spark then the test name would be adjusted to be foo [linux, spark]

This setting can also be set using a system property or environment variable kotest.framework.testname.append.tags to true.

Test name whitespace

If you define test names over several lines then removeTestNameWhitespace can be useful. Take this example:

"""this is
   my test case""" {
  // test here
}

Then the test name in output will be this is my test case. By setting removeTestNameWhitespace to true, then this name will be trimmed to this is my test case.

An alternative way to enable this is by setting system property kotest.framework.testname.multiline to true which will always (if defined) take priority over the value here.

object KotestProjectConfig : AbstractProjectConfig() {
    override val testNameRemoveWhitespace = true
}