Suppress reported exceptions in runTest

Author: dkhalanskyjb

kotlinx-coroutines-test/common/src/TestBuilders.kt

@@ -148,7 +148,8 @@ public expect class TestResult
  * #### Reported exceptions
  *
  * Exceptions reported to the test coroutine scope via [TestCoroutineScope.reportException] will be thrown at the end.
- * By default, unless an explicit [TestExceptionHandler] is passed, this includes all unhandled exceptions.
+ * By default, unless an explicit [TestExceptionHandler] is passed, this includes all unhandled exceptions. If the test
+ * body also fails, the reported exceptions are suppressed by it.
  *
  * #### Uncompleted coroutines
  *
@@ -219,7 +220,7 @@ public fun runTest(
             } catch (e: UncompletedCoroutinesError) {
                 // it's normal that some jobs are not completed if the test body has failed, won't clutter the output
             } catch (e: Throwable) {
-                e.printStackTrace()
+                it.addSuppressed(e)
             }
             throw it
         }

kotlinx-coroutines-test/common/test/RunTestTest.kt

@@ -216,4 +216,28 @@ class RunTestTest {
             }
         }
     })
+
+    /** Tests that, when the test body fails, the reported exceptions are suppressed. */
+    @Test
+    fun testSuppressedExceptions() = testResultMap({
+        try {
+            it()
+            fail("should not be reached")
+        } catch (e: TestException) {
+            assertEquals("w", e.message)
+            val suppressed = e.suppressedExceptions +
+                (e.suppressedExceptions.firstOrNull()?.suppressedExceptions ?: emptyList())
+            assertEquals(3, suppressed.size)
+            assertEquals("x", suppressed[0].message)
+            assertEquals("y", suppressed[1].message)
+            assertEquals("z", suppressed[2].message)
+        }
+    }, {
+        runTest {
+            reportException(TestException("x"))
+            reportException(TestException("y"))
+            reportException(TestException("z"))
+            throw TestException("w")
+        }
+    })
 }