Add Raise matchers (#262)

Co-authored-by: Tim Grafford <[email protected]>

kotest-assertions-arrow/src/commonMain/kotlin/io/kotest/assertions/arrow/core/Raise.kt

@@ -0,0 +1,49 @@
+package io.kotest.assertions.arrow.core
+
+import arrow.core.raise.Raise
+import arrow.core.raise.recover
+import io.kotest.assertions.failure
+import io.kotest.assertions.print.print
+
+/**
+ * Verifies if a block of code will raise a specified type of [T] (or subclasses).
+ *
+ * This function will include subclasses of [T]. For example, if you test for [CharSequence] and the code raises
+ * [String], the test will pass.
+ *
+ * ```kotlin
+ * val raised: String = shouldRaise<String> {
+ *   raise("failed")
+ * }
+ * ```
+ */
+public suspend inline fun <reified T> shouldRaise(noinline block: suspend Raise<Any?>.() -> Any?): T {
+  val expectedRaiseClass = T::class
+  return recover({
+    block()
+    throw failure("Expected to raise ${expectedRaiseClass.simpleName} but nothing was raised.")
+  }) { raised ->
+    when (raised) {
+      is T -> raised
+      null -> throw failure("Expected to raise ${expectedRaiseClass.simpleName} but <null> was raised instead.")
+      else -> throw failure("Expected to raise ${expectedRaiseClass.simpleName} but ${raised::class.simpleName} was raised instead.")
+    }
+  }
+}
+
+/**
+ * Verifies that a block of code will not raise anything.
+ *
+ * ```kotlin
+ * val raised: String = shouldNotRaise {
+ *   raise("failed") // fails
+ * }
+ * ```
+ */
+public suspend fun <T> shouldNotRaise(block: suspend Raise<Any?>.() -> T): T {
+  return recover({
+    block()
+  }) { raised ->
+    throw failure("No raise expected, but ${raised.print().value} was raised.")
+  }
+}

kotest-assertions-arrow/src/commonTest/kotlin/io/kotest/assertions/arrow/core/RaiseMatchers.kt

@@ -0,0 +1,75 @@
+package io.kotest.assertions.arrow.core
+
+import io.kotest.assertions.arrow.shouldBe
+import io.kotest.assertions.throwables.shouldThrowWithMessage
+import io.kotest.core.spec.style.StringSpec
+
+class RaiseMatchers : StringSpec({
+  "shouldRaise: specific type" {
+    val raised = shouldRaise<String> {
+      raise("failed")
+    }
+    raised shouldBe "failed"
+  }
+
+  "shouldRaise: subtype" {
+    val raised = shouldRaise<CharSequence> {
+      raise("failed")
+    }
+    raised shouldBe "failed"
+  }
+
+  "shouldRaise: nullable type" {
+    val raised = shouldRaise<String?> {
+      raise(null)
+    }
+    raised shouldBe null
+  }
+
+  "shouldRaise: fail if null is raised when not expected" {
+    shouldThrowWithMessage<AssertionError>("Expected to raise String but <null> was raised instead.") {
+      shouldRaise<String> {
+        raise(null)
+      }
+    }
+  }
+
+  "shouldRaise: fail if expected raise type differs from actual" {
+    shouldThrowWithMessage<AssertionError>("Expected to raise Int but String was raised instead.") {
+      shouldRaise<Int> {
+        raise("failed")
+      }
+    }
+  }
+
+  "shouldRaise: fail if nothing is raised" {
+    shouldThrowWithMessage<AssertionError>("Expected to raise Int but nothing was raised.") {
+      shouldRaise<Int> {
+        42
+      }
+    }
+  }
+
+  "shouldNotRaise" {
+    val res = shouldNotRaise {
+      42
+    }
+    res shouldBe 42
+  }
+
+  "shouldNotRaise: fail if something is raised" {
+    shouldThrowWithMessage<AssertionError>("No raise expected, but \"failed\" was raised.") {
+      shouldNotRaise {
+        raise("failed")
+      }
+    }
+  }
+
+  "shouldNotRaise: fail if null was raised" {
+    shouldThrowWithMessage<AssertionError>("No raise expected, but <null> was raised.") {
+      shouldNotRaise {
+        raise(null)
+      }
+    }
+  }
+})