Clean up tests asserting failure states: introduce an 'assertThrows()' assertion inspired by a similar assertion in JUnit5. The new assertion function asserts an exception of the given type is thrown by the block lambda and the exception is returned for further assertions.

Author: m-koops

tests/src/test/kotlin/test/JUnit4Utils.kt

@@ -0,0 +1,13 @@
+package test
+
+import junit.framework.AssertionFailedError
+
+/** Inspired by JUnit5, asserts an exception being thrown */
+inline fun <reified E: Throwable> assertThrows(block: () -> Unit): E {
+    return try {
+        block.invoke()
+        throw AssertionFailedError("No exception of type ${(E::class).simpleName} was thrown")
+    } catch (e: Throwable) {
+        e as? E ?: throw e
+    }
+}

tests/src/test/kotlin/test/MockingTest.kt

@@ -180,16 +180,14 @@ class MockingTest : TestBase() {
         System.setOut(out)
         val mock = mock<SynchronousFunctions>(verboseLogging = true)
 
-        try {
-            /* When */
+
+        /* When, Then */
+        assertThrows<WantedButNotInvoked> {
             verify(mock).stringResult()
-            fail("Expected an exception")
-        } catch (_: WantedButNotInvoked) {
-            /* Then */
-            argumentCaptor<DescribedInvocation>().apply {
-                verify(out).println(capture())
-                expect(lastValue.toString()).toBe("synchronousFunctions.stringResult();")
-            }
+        }
+        argumentCaptor<DescribedInvocation>().apply {
+            verify(out).println(capture())
+            expect(lastValue.toString()).toBe("synchronousFunctions.stringResult();")
         }
     }
 

tests/src/test/kotlin/test/OngoingStubbingTest.kt

@@ -2,7 +2,6 @@ package test
 
 import com.nhaarman.expect.expect
 import com.nhaarman.expect.expectErrorWithMessage
-import com.nhaarman.expect.fail
 import org.junit.Assume.assumeFalse
 import org.junit.Test
 import org.mockito.Mockito
@@ -64,11 +63,9 @@ class OngoingStubbingTest : TestBase() {
             on { builderMethod() } doThrow IllegalArgumentException()
         }
 
-        try {
-            /* When */
+        /* When, Then */
+        assertThrows<IllegalArgumentException> {
             mock.builderMethod()
-            fail("No exception thrown")
-        } catch (_: IllegalArgumentException) {
         }
     }
 
@@ -79,11 +76,9 @@ class OngoingStubbingTest : TestBase() {
             on { builderMethod() } doThrow IllegalArgumentException::class
         }
 
-        try {
-            /* When */
+        /* When, Then */
+        assertThrows<IllegalArgumentException> {
             mock.builderMethod()
-            fail("No exception thrown")
-        } catch (_: IllegalArgumentException) {
         }
     }
 
@@ -97,18 +92,12 @@ class OngoingStubbingTest : TestBase() {
             )
         }
 
-        try {
-            /* When */
+        /* When, Then */
+        assertThrows<IllegalArgumentException> {
             mock.builderMethod()
-            fail("No exception thrown")
-        } catch (_: IllegalArgumentException) {
         }
-
-        try {
-            /* When */
+        assertThrows<UnsupportedOperationException> {
             mock.builderMethod()
-            fail("No exception thrown")
-        } catch (_: UnsupportedOperationException) {
         }
     }
 
@@ -122,18 +111,12 @@ class OngoingStubbingTest : TestBase() {
             )
         }
 
-        try {
-            /* When */
+        /* When, Then */
+        assertThrows<IllegalArgumentException> {
             mock.builderMethod()
-            fail("No exception thrown")
-        } catch (_: IllegalArgumentException) {
         }
-
-        try {
-            /* When */
+        assertThrows<UnsupportedOperationException> {
             mock.builderMethod()
-            fail("No exception thrown")
-        } catch (_: UnsupportedOperationException) {
         }
     }