Set assertion error message as message attr in <failure>

internal/command/junit/junit.go

@@ -239,8 +239,9 @@ func junitXMLTestReport(suite *moduletest.Suite, suiteRunnerStopped bool, source
 						delete(diagsMap, key)
 					}
 				}
+				msg := getFailMessage(diagsStr.String())
 				testCase.Failure = &withMessage{
-					Message: "Test run failed",
+					Message: msg,
 					Body:    diagsStr.String(),
 				}
 			case moduletest.Error:
@@ -281,6 +282,17 @@ func junitXMLTestReport(suite *moduletest.Suite, suiteRunnerStopped bool, source
 	return buf.Bytes(), nil
 }
 
+func getFailMessage(diagsStr string) string {
+	diagLines := strings.Split(diagsStr, "\n")
+	for i := len(diagLines) - 1; i >= 0; i-- {
+		if diagLines[i] != "" {
+			return diagLines[i]
+		}
+	}
+
+	return ""
+}
+
 // getSkipDetails checks data about the test suite, file and runs to determine why a given run was skipped
 // Test can be skipped due to:
 // 1. terraform test recieving an interrupt from users; all unstarted tests will be skipped