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Added contracts for kotlin assertions
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Added assertNull and assertNotNull methods with contracts.
Added contracts for assertThrows and assertDoesNotThrow methods.

assertInstanceOf can be implemented only with kotlin 1.4, because
refined generics
[are not supported](https://youtrack.jetbrains.com/issue/KT-28298)
in contracts for kotlin 1.3 yet.

Issue: junit-team#1866
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@awelless
awelless committed Apr 7, 2023
1 parent e188b1e commit 914babd
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Showing 3 changed files with 266 additions and 20 deletions.
8 changes: 8 additions & 0 deletions junit-jupiter-api/junit-jupiter-api.gradle.kts
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Original file line number Diff line number Diff line change
Expand Up @@ -30,3 +30,11 @@ tasks {
}
}
}

kotlin {
sourceSets {
main {
languageSettings.optIn("kotlin.contracts.ExperimentalContracts")
}
}
}
238 changes: 218 additions & 20 deletions junit-jupiter-api/src/main/kotlin/org/junit/jupiter/api/Assertions.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,9 @@ import org.junit.jupiter.api.function.ThrowingSupplier
import java.time.Duration
import java.util.function.Supplier
import java.util.stream.Stream
import kotlin.contracts.InvocationKind.AT_MOST_ONCE
import kotlin.contracts.InvocationKind.EXACTLY_ONCE
import kotlin.contracts.contract

/**
* @see Assertions.fail
Expand Down Expand Up @@ -86,6 +89,139 @@ fun assertAll(vararg executables: () -> Unit) =
fun assertAll(heading: String?, vararg executables: () -> Unit) =
assertAll(heading, executables.toList().stream())

/**
* Example usage:
* ```kotlin
* val string: String? = ...
*
* assertNull(string)
*
* // compiler won't allow even safe calls, since the string is always null
* // string?.isNotEmpty()
* ```
* @see Assertions.assertNull
*/
@API(since = "5.10", status = STABLE)
fun assertNull(actual: Any?) {
contract {
returns() implies (actual == null)
}

Assertions.assertNull(actual)
}

/**
* Example usage:
* ```kotlin
* val string: String? = ...
*
* assertNull(string, "Should be nullable")
*
* // compiler won't allow even safe calls, since the string is always null
* // string?.isNotEmpty()
* ```
* @see Assertions.assertNull
*/
@API(since = "5.10", status = STABLE)
fun assertNull(actual: Any?, message: String) {
contract {
returns() implies (actual == null)
}

Assertions.assertNull(actual, message)
}

/**
* Example usage:
* ```kotlin
* val string: String? = ...
*
* assertNull(string) { "Should be nullable" }
*
* // compiler won't allow even safe calls, since the string is always null
* // string?.isNotEmpty()
* ```
* @see Assertions.assertNull
*/
@API(since = "5.10", status = STABLE)
fun assertNull(actual: Any?, messageSupplier: () -> String) {
contract {
returns() implies (actual == null)

callsInPlace(messageSupplier, AT_MOST_ONCE)
}

Assertions.assertNull(actual, messageSupplier)
}

/**
* Example usage:
* ```kotlin
* val string: String? = ...
*
* assertNotNull(string)
*
* // compiler smart casts nullableString to a non-nullable object
* assertTrue(string.isNotEmpty())
* ```
* @see Assertions.assertNotNull
*/
@API(since = "5.10", status = STABLE)
fun <T> assertNotNull(actual: T?): T {
contract {
returns() implies (actual != null)
}

Assertions.assertNotNull(actual)
return actual!!
}

/**
* Example usage:
* ```kotlin
* val string: String? = ...
*
* assertNotNull(string, "Should be non-nullable")
*
* // compiler smart casts nullableString to a non-nullable object
* assertTrue(string.isNotEmpty())
* ```
* @see Assertions.assertNotNull
*/
@API(since = "5.10", status = STABLE)
fun <T> assertNotNull(actual: T?, message: String): T {
contract {
returns() implies (actual != null)
}

Assertions.assertNotNull(actual, message)
return actual!!
}

/**
* Example usage:
* ```kotlin
* val string: String? = ...
*
* assertNotNull(string) { "Should be non-nullable" }
*
* // compiler smart casts nullableString to a non-nullable object
* assertTrue(string.isNotEmpty())
* ```
* @see Assertions.assertNotNull
*/
@API(since = "5.10", status = STABLE)
fun <T> assertNotNull(actual: T?, messageSupplier: () -> String): T {
contract {
returns() implies (actual != null)

callsInPlace(messageSupplier, AT_MOST_ONCE)
}

Assertions.assertNotNull(actual, messageSupplier)
return actual!!
}

/**
* Example usage:
* ```kotlin
Expand All @@ -97,6 +233,10 @@ fun assertAll(heading: String?, vararg executables: () -> Unit) =
* @see Assertions.assertThrows
*/
inline fun <reified T : Throwable> assertThrows(executable: () -> Unit): T {
contract {
callsInPlace(executable, EXACTLY_ONCE)
}

val throwable: Throwable? = try {
executable()
} catch (caught: Throwable) {
Expand All @@ -120,8 +260,13 @@ inline fun <reified T : Throwable> assertThrows(executable: () -> Unit): T {
* ```
* @see Assertions.assertThrows
*/
inline fun <reified T : Throwable> assertThrows(message: String, executable: () -> Unit): T =
assertThrows({ message }, executable)
inline fun <reified T : Throwable> assertThrows(message: String, executable: () -> Unit): T {
contract {
callsInPlace(executable, EXACTLY_ONCE)
}

return assertThrows({ message }, executable)
}

/**
* Example usage:
Expand All @@ -134,6 +279,11 @@ inline fun <reified T : Throwable> assertThrows(message: String, executable: ()
* @see Assertions.assertThrows
*/
inline fun <reified T : Throwable> assertThrows(noinline message: () -> String, executable: () -> Unit): T {
contract {
callsInPlace(executable, EXACTLY_ONCE)
callsInPlace(message, AT_MOST_ONCE)
}

val throwable: Throwable? = try {
executable()
} catch (caught: Throwable) {
Expand Down Expand Up @@ -162,8 +312,13 @@ inline fun <reified T : Throwable> assertThrows(noinline message: () -> String,
* @param R the result type of the [executable]
*/
@API(status = EXPERIMENTAL, since = "5.5")
inline fun <R> assertDoesNotThrow(executable: () -> R): R =
Assertions.assertDoesNotThrow(evaluateAndWrap(executable))
inline fun <R> assertDoesNotThrow(executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
}

return Assertions.assertDoesNotThrow(evaluateAndWrap(executable))
}

/**
* Example usage:
Expand All @@ -176,8 +331,13 @@ inline fun <R> assertDoesNotThrow(executable: () -> R): R =
* @param R the result type of the [executable]
*/
@API(status = EXPERIMENTAL, since = "5.5")
inline fun <R> assertDoesNotThrow(message: String, executable: () -> R): R =
assertDoesNotThrow({ message }, executable)
inline fun <R> assertDoesNotThrow(message: String, executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
}

return assertDoesNotThrow({ message }, executable)
}

/**
* Example usage:
Expand All @@ -190,11 +350,17 @@ inline fun <R> assertDoesNotThrow(message: String, executable: () -> R): R =
* @param R the result type of the [executable]
*/
@API(status = EXPERIMENTAL, since = "5.5")
inline fun <R> assertDoesNotThrow(noinline message: () -> String, executable: () -> R): R =
Assertions.assertDoesNotThrow(
inline fun <R> assertDoesNotThrow(noinline message: () -> String, executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
callsInPlace(message, AT_MOST_ONCE)
}

return Assertions.assertDoesNotThrow(
evaluateAndWrap(executable),
Supplier(message)
)
}

@PublishedApi
internal inline fun <R> evaluateAndWrap(executable: () -> R): ThrowingSupplier<R> = try {
Expand All @@ -215,8 +381,13 @@ internal inline fun <R> evaluateAndWrap(executable: () -> R): ThrowingSupplier<R
* @paramR the result of the [executable].
*/
@API(status = EXPERIMENTAL, since = "5.5")
fun <R> assertTimeout(timeout: Duration, executable: () -> R): R =
Assertions.assertTimeout(timeout, executable)
fun <R> assertTimeout(timeout: Duration, executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
}

return Assertions.assertTimeout(timeout, executable)
}

/**
* Example usage:
Expand All @@ -229,8 +400,13 @@ fun <R> assertTimeout(timeout: Duration, executable: () -> R): R =
* @paramR the result of the [executable].
*/
@API(status = EXPERIMENTAL, since = "5.5")
fun <R> assertTimeout(timeout: Duration, message: String, executable: () -> R): R =
Assertions.assertTimeout(timeout, executable, message)
fun <R> assertTimeout(timeout: Duration, message: String, executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
}

return Assertions.assertTimeout(timeout, executable, message)
}

/**
* Example usage:
Expand All @@ -243,8 +419,14 @@ fun <R> assertTimeout(timeout: Duration, message: String, executable: () -> R):
* @paramR the result of the [executable].
*/
@API(status = EXPERIMENTAL, since = "5.5")
fun <R> assertTimeout(timeout: Duration, message: () -> String, executable: () -> R): R =
Assertions.assertTimeout(timeout, executable, message)
fun <R> assertTimeout(timeout: Duration, message: () -> String, executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
callsInPlace(message, AT_MOST_ONCE)
}

return Assertions.assertTimeout(timeout, executable, message)
}

/**
* Example usage:
Expand All @@ -257,8 +439,13 @@ fun <R> assertTimeout(timeout: Duration, message: () -> String, executable: () -
* @paramR the result of the [executable].
*/
@API(status = EXPERIMENTAL, since = "5.5")
fun <R> assertTimeoutPreemptively(timeout: Duration, executable: () -> R): R =
Assertions.assertTimeoutPreemptively(timeout, executable)
fun <R> assertTimeoutPreemptively(timeout: Duration, executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
}

return Assertions.assertTimeoutPreemptively(timeout, executable)
}

/**
* Example usage:
Expand All @@ -271,8 +458,13 @@ fun <R> assertTimeoutPreemptively(timeout: Duration, executable: () -> R): R =
* @paramR the result of the [executable].
*/
@API(status = EXPERIMENTAL, since = "5.5")
fun <R> assertTimeoutPreemptively(timeout: Duration, message: String, executable: () -> R): R =
Assertions.assertTimeoutPreemptively(timeout, executable, message)
fun <R> assertTimeoutPreemptively(timeout: Duration, message: String, executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
}

return Assertions.assertTimeoutPreemptively(timeout, executable, message)
}

/**
* Example usage:
Expand All @@ -285,5 +477,11 @@ fun <R> assertTimeoutPreemptively(timeout: Duration, message: String, executable
* @paramR the result of the [executable].
*/
@API(status = EXPERIMENTAL, since = "5.5")
fun <R> assertTimeoutPreemptively(timeout: Duration, message: () -> String, executable: () -> R): R =
Assertions.assertTimeoutPreemptively(timeout, executable, message)
fun <R> assertTimeoutPreemptively(timeout: Duration, message: () -> String, executable: () -> R): R {
contract {
callsInPlace(executable, EXACTLY_ONCE)
callsInPlace(message, AT_MOST_ONCE)
}

return Assertions.assertTimeoutPreemptively(timeout, executable, message)
}
40 changes: 40 additions & 0 deletions junit-jupiter-engine/src/test/kotlin/org/junit/jupiter/api/KotlinAssertionsTests.kt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -211,6 +211,46 @@ class KotlinAssertionsTests {
assertMessageStartsWith(error, assertionMessage)
}

@Test
fun `assertNotNull with compiler smart cast`() {
val nullableString: String? = "string"

assertNotNull(nullableString)
assertFalse(nullableString.isEmpty()) // smart cast to non nullable object
}

@Test
fun `assertNull with compiler smart cast`() {
val nullableString: String? = null

assertNull(nullableString)
// even safe call is not allowed, because compiler knows that string is always null
// nullableString?.isEmpty()
}

@Test
fun `assertThrows with value initialization in lambda`() {
val value: String

assertThrows<AssertionError> {
value = "string"
Assertions.fail("message")
}

assertEquals("string", value)
}

@Test
fun `assertDoesNotThrow with value initialization in lambda`() {
val value: Int

assertDoesNotThrow {
value = 10
}

assertEquals(10, value)
}

companion object {
fun assertExpectedExceptionTypes(
multipleFailuresError: MultipleFailuresError,
Expand Down

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