Merge pull request #1 from xemantic/feature/basicAssertFunction

Basic assert function

README.md

@@ -7,7 +7,7 @@ Kotlin multiplatform testing library providing power-assert compatible DSL and a
 I am mostly using [kotest](https://kotest.io/) library for writing test assertions
 in my projects. When [power-assert](https://kotlinlang.org/docs/power-assert.html)
 became the official Kotlin compiler plugin, I also realized that most of the kotest
-assertions can be replaced with something which suits my purposes better.
+assertions can be replaced with something which suits my needs much better.
 Instead of writing:
 
 ```kotlin
@@ -20,14 +20,8 @@ I could write:
 assert(x >= 42)
 ```
 
-Unfortunately the [assert](https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/assert.html)
-function is supported at the moment only for `JVM` and `Native` out of all the Kotlin
-multiplatform targets. So for my multiplatform libraries it would rather be
-[assertTrue](https://kotlinlang.org/api/core/kotlin-test/kotlin.test/assert-true.html), but
-... it is becoming too verbose.
-
-Quite often I am asserting the state of hierarchical data
-structures, therefore I came up with this syntax:
+Next to this, I am quite often asserting the state of hierarchical data
+structures, therefore I came up with such a syntax:
 
 ```kotlin
 message should {
@@ -122,6 +116,18 @@ powerAssert {
 
 ### Basic Assertions
 
+```kotlin
+assert(2 + 2 == 4)
+```
+
+> [!NOTE]
+> The [assert](https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/assert.html)
+> function in Kotlin stdlib is providing `assert` only for `JVM` and `Native` out of all the Kotlin
+> multiplatform targets. The multiplatform `assert` function can be
+> imported from `com.xemantic.kotlin.test.assert`
+
+### Asserting object properties
+
 The library introduces the [should](src/commonMain/kotlin/Assertions.kt) infix function, which allows you to chain assertions on an object:
 
 ```kotlin

api/xemantic-kotlin-test.api

@@ -1,4 +1,6 @@
 public final class com/xemantic/kotlin/test/AssertionsKt {
+	public static final fun assert (ZLjava/lang/String;)V
+	public static synthetic fun assert$default (ZLjava/lang/String;ILjava/lang/Object;)V
 	public static final fun have (ZLjava/lang/String;)V
 	public static synthetic fun have$default (ZLjava/lang/String;ILjava/lang/Object;)V
 	public static final fun should (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)V

build.gradle.kts

@@ -147,6 +147,7 @@ tasks.withType<Test> {
 
 powerAssert {
   functions = listOf(
+    "com.xemantic.kotlin.test.assert",
     "com.xemantic.kotlin.test.have"
   )
 }

src/commonMain/kotlin/Assertions.kt

@@ -22,6 +22,15 @@ import kotlin.contracts.contract
 import kotlin.reflect.typeOf
 import kotlin.test.assertNotNull
 import kotlin.test.assertTrue
+import kotlin.test.asserter
+
+@OptIn(ExperimentalContracts::class)
+public fun assert(actual: Boolean, message: String? = null) {
+  contract {
+    returns() implies actual
+  }
+  return asserter.assertTrue(message ?: "Expected value to be true.", actual)
+}
 
 @OptIn(ExperimentalContracts::class)
 public infix fun <T> T?.should(block: T.() -> Unit) {

src/commonTest/kotlin/AssertionsTest.kt

@@ -208,4 +208,23 @@ class AssertionsTest {
     )
   }
 
+  @Test
+  fun `Should fail when assertion resolves to false`() {
+    val exception = assertFailsWith<AssertionError> {
+      assert(2 + 2 == 2 + 3)
+    }
+    assertEquals(
+      expected = """
+        |
+        |assert(2 + 2 == 2 + 3)
+        |         |   |    |
+        |         |   |    5
+        |         |   false
+        |         4
+        |
+      """.trimMargin(),
+      actual = exception.message
+    )
+  }
+
 }