Kotest Resources

This page explains how to automatically close resources in Kotest and how to temporarily create files and directories needed for tests.
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Closing Resources Automatically

You can have Kotest automatically close resources after all tests have run.

Kotest’s autoClose function lets you automatically release a specific resource after use, making resource management easier. It is mainly used when tests use external resources, and it can release those resources automatically without requiring explicit cleanup.

For example, when a test uses an external resource such as a file or database connection, that resource must normally be released explicitly after use. With autoClose, the resource is released when the test finishes.

package com.devkuma.kotest.tutorial.resources

import io.kotest.core.spec.style.StringSpec
import io.kotest.matchers.shouldBe
import java.io.StringReader

class StringTest : StringSpec({

    val reader = autoClose(StringReader("xyz"))

    "test" {
        val text = reader.readText()

        println(text)

        text shouldBe "xyz"
    }
})

Resources closed this way must implement java.lang.AutoCloseable. Closing is performed in reverse declaration order after the final spec interceptor returns.

Temporary Files

Sometimes a test needs to create a file and delete it afterward, but manual deletion can fail if the test fails.

For example, if a temporary file is created during a test and the test passes successfully, cleanup code runs and deletes the file. However, if an assertion fails or another error occurs and the file is not deleted, a stale file may affect the next run, for example by causing a file overwrite exception.

Kotest provides a tempfile() function that can be used to create temporary files for tests in a spec. Kotest cleans up these files after all tests in the spec have run. This means you do not need to worry about deleting temporary files in tests.

package com.devkuma.kotest.tutorial.resources

import io.kotest.core.spec.style.FunSpec
import io.kotest.engine.spec.tempfile
import io.kotest.matchers.shouldBe
import java.io.FileReader

class TempFileTest : FunSpec({

    val file = tempfile()

    test("a temporary file dependent test") {
        // file path
        println(file.path)

        // write file
        val text = "Hello, Kotest!"
        file.writeText(text)

        // read file
        val reader = autoClose(FileReader(file))
        reader.readText() shouldBe text
    }
})

Temporary Directories

Like temporary files, you can create a temporary directory with tempdir().

package com.devkuma.kotest.tutorial.resources

import io.kotest.core.spec.style.FunSpec
import io.kotest.engine.spec.tempdir
import io.kotest.matchers.shouldBe

class TempDirTest : FunSpec({

    val dir = tempdir()

    test("a temporary dir dependent test") {
        println(dir.path)

        dir.isDirectory shouldBe true
    }
})

References