(#) platform types should not be mocked !!! ERROR: platform types should not be mocked This is an error. Id : `DoNotMockPlatformTypes` Summary : platform types should not be mocked Severity : Error Category : Correctness Platform : Any Vendor : slack Identifier : slack-lint Contact : https://github.com/slackhq/slack-lints Feedback : https://github.com/slackhq/slack-lints Min : Lint 8.7+ Compiled : Lint 8.7+ Artifact : [com.slack.lint:slack-lint-checks](com_slack_lint_slack-lint-checks.md.html) Since : 0.4.0 Affects : Kotlin and Java files and test sources Editing : This check runs on the fly in the IDE editor Implementation : [Source Code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/main/java/slack/lint/mocking/MockDetector.kt) Tests : [Source Code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/test/java/slack/lint/mocking/MockDetectorOptionsTest.kt) Copyright Year : 2021 Platform types (i.e. classes in java.*, android.*, etc) should not be mocked. Use a real instance or fake instead. Mocking platform types like these can lead to surprising test failures due to mocks that actually behave differently than real instances, especially when passed into real implementations that use them and expect them to behave in a certain way. If using Robolectric, consider using its shadow APIs. (##) Options You can configure this lint checks using the following options: (###) mock-annotations A comma-separated list of mock annotations.. This property should define comma-separated list of mock annotation class names (FQCN). Set this for all issues using this option. Default is "org.mockito.Mock,org.mockito.Spy". Example `lint.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <lint> <issue id="DoNotMockPlatformTypes"> <option name="mock-annotations" value=""org.mockito.Mock,org.mockito.Spy"" /> </issue> </lint> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (###) mock-factories A comma-separated list of mock factories (org.mockito.Mockito#methodName).. A comma-separated list of mock factories (org.mockito.Mockito#methodName). Set this for all issues using this option. Default is "org.mockito.Mockito#mock,org.mockito.Mockito#spy,slack.test.mockito.MockitoHelpers#mock,slack.test.mockito.MockitoHelpersKt#mock,org.mockito.kotlin.MockingKt#mock,org.mockito.kotlin.SpyingKt#spy". Example `lint.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <lint> <issue id="DoNotMockPlatformTypes"> <option name="mock-factories" value=""org.mockito.Mockito#mock,org.mockito.Mockito#spy,slack.test.mockito.MockitoHelpers#mock,slack.test.mockito.MockitoHelpersKt#mock,org.mockito.kotlin.MockingKt#mock,org.mockito.kotlin.SpyingKt#spy"" /> </issue> </lint> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (###) mock-report If enabled, writes a mock report to /build/reports/mockdetector/mock-report.csv.. If enabled, writes a mock report to /build/reports/mockdetector/mock-report.csv. The format of the file is a csv of (type,isError) of mocked classes. Set this for all issues using this option. Default is "none". Example `lint.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <lint> <issue id="DoNotMockPlatformTypes"> <option name="mock-report" value=""none"" /> </issue> </lint> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text test/slack/test/MyTests.kt:62:Error: platform type 'java.lang.Comparable' should not be mocked [DoNotMockPlatformTypes] mockk<Comparable<String>>() --------------------------- test/slack/test/MyTests.kt:63:Error: platform type 'java.lang.Runnable' should not be mocked [DoNotMockPlatformTypes] mockk<Runnable>() ----------------- test/slack/test/MyTests.kt:65:Error: platform type 'kotlin.io.FileTreeWalk' should not be mocked [DoNotMockPlatformTypes] mockk<FileTreeWalk>() --------------------- test/slack/test/MyTests.kt:66:Error: platform type 'kotlin.Lazy' should not be mocked [DoNotMockPlatformTypes] mockk<Lazy<String>>() --------------------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is the source file referenced above: `test/slack/test/MyTests.kt`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers package slack.test import io.mockk.impl.annotations.MockK import io.mockk.impl.annotations.SpyK import io.mockk.mockk import io.mockk.mockkClass import io.mockk.mockkObject import io.mockk.spyk class MyTests { @MockK lateinit var fieldDataMock: DataClass @SpyK lateinit var fieldDataSpy: DataClass fun dataClass() { val localMock1: DataClass = mockk() val localMock2 = mockk() val localSpy1: DataClass = spyk() val localSpy2 = spyk() val localSpy3 = spyk(localMock1) // KClass is not detected, explicit type needed! val localClassMock = mockkClass(DataClass::class) } @MockK lateinit var fieldSealedMock: SealedClass @SpyK lateinit var fieldSealedSpy: SealedClass fun sealedClass() { val localMock1: SealedClass = mockk() val localMock2 = mockk() val localSpy1: SealedClass = spyk() val localSpy2 = spyk() val localSpy3 = spyk(localMock1) // KClass is not detected, explicit type needed! val localClassMock = mockkClass(SealedClass::class) } @MockK lateinit var fieldObjectMock: ObjectClass @SpyK lateinit var fieldObjectSpy: ObjectClass fun objectClass() { val localMock1: ObjectClass = mockk() val localMock2 = mockk() val localSpy1: ObjectClass = spyk() val localSpy2 = spyk() val localSpy3 = spyk(localMock1) // KClass is not detected, explicit type needed! val localClassMock = mockkClass(ObjectClass::class) // Wrong Error: 'kotlin.Unit' is an object, so mocking it should not be necessary [DoNotMockObjectClass] // Wrong Warning: platform type 'kotlin.Unit' should not be mocked [DoNotMockPlatformTypes] // mockkObject(ObjectClass) } fun platformTypes() { // java. mockk>() mockk() // kotlin. mockk() mockk>() } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://github.com/slackhq/slack-lints/tree/main/slack-lint-checks/src/test/java/slack/lint/mocking/MockDetectorOptionsTest.kt) for the unit tests for this check to see additional scenarios. The above example was automatically extracted from the first unit test found for this lint check, `MockDetector.tests`. To report a problem with this extracted sample, visit https://github.com/slackhq/slack-lints. (##) Including !!! This is not a built-in check. To include it, add the below dependency to your project. This lint check is included in the lint documentation, but the Android team may or may not agree with its recommendations. ``` // build.gradle.kts lintChecks("com.slack.lint:slack-lint-checks:0.9.0") // build.gradle lintChecks 'com.slack.lint:slack-lint-checks:0.9.0' // build.gradle.kts with version catalogs: lintChecks(libs.slack.lint.checks) # libs.versions.toml [versions] slack-lint-checks = "0.9.0" [libraries] # For clarity and text wrapping purposes the following declaration is # shown split up across lines, but in TOML it needs to be on a single # line (see https://github.com/toml-lang/toml/issues/516) so adjust # when pasting into libs.versions.toml: slack-lint-checks = { module = "com.slack.lint:slack-lint-checks", version.ref = "slack-lint-checks" } ``` 0.9.0 is the version this documentation was generated from; there may be newer versions available. [Additional details about com.slack.lint:slack-lint-checks](com_slack_lint_slack-lint-checks.md.html). (##) Suppressing You can suppress false positives using one of the following mechanisms: * Using a suppression annotation like this on the enclosing element: ```kt // Kotlin @Suppress("DoNotMockPlatformTypes") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("DoNotMockPlatformTypes") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection DoNotMockPlatformTypes problematicStatement() ``` * Using a special `lint.xml` file in the source tree which turns off the check in that folder and any sub folder. A simple file might look like this: ```xml <?xml version="1.0" encoding="UTF-8"?> <lint> <issue id="DoNotMockPlatformTypes" severity="ignore" /> </lint> ``` Instead of `ignore` you can also change the severity here, for example from `error` to `warning`. You can find additional documentation on how to filter issues by path, regular expression and so on [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html). * In Gradle projects, using the DSL syntax to configure lint. For example, you can use something like ```gradle lintOptions { disable 'DoNotMockPlatformTypes' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore DoNotMockPlatformTypes ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).