Line matcher should return an error instead of panic

Author: SimonBaeumer

pkg/runtime/validator.go

@@ -137,12 +137,25 @@ func validateExpectedLines(got string, expected ExpectedOut) matcher.MatcherResu
 	actualLines := strings.Split(got, getLineBreak())
 	result := matcher.MatcherResult{Success: true}
 
-	for k, expL := range expected.Lines {
-		if (k-1 > len(actualLines)) || (k-1 < 0) {
-			panic(fmt.Sprintf("Invalid line number given %d", k))
+	for key, expectedLine := range expected.Lines {
+		// line number 0 or below 0
+		if key <= 0 {
+			panic(fmt.Sprintf("Invalid line number given %d", key))
 		}
 
-		if result = m.Match(actualLines[k-1], expL); !result.Success {
+		// line number exceeds result set
+		if key > len(actualLines) {
+			return matcher.MatcherResult{
+				Success: false,
+				Diff: fmt.Sprintf(
+					"Line number %d does not exists in result: \n\n%s",
+					key-1,
+					strings.Join(actualLines, "\n"),
+				),
+			}
+		}
+
+		if result = m.Match(actualLines[key-1], expectedLine); !result.Success {
 			return result
 		}
 	}

pkg/runtime/validator_test.go

@@ -94,17 +94,31 @@ output`
 	assert.Empty(t, got.Diff)
 }
 
+func Test_ValidateExpectedOut_MatchLines_ExpectedLineDoesNotExists(t *testing.T) {
+	value := `test`
+
+	got := validateExpectedOut(value, ExpectedOut{Lines: map[int]string{2: "my", 3: "line"}})
+
+	assert.False(t, got.Success)
+	diff := `Line number 1 does not exists in result: 
+
+test`
+	assert.Equal(t, diff, got.Diff)
+}
+
 func Test_ValidateExpectedOut_MatchLines_Fails(t *testing.T) {
-	value := ``
+	value := `test
+line 2
+line 3`
 
-	got := validateExpectedOut(value, ExpectedOut{Lines: map[int]string{1: "my", 3: "line"}})
+	got := validateExpectedOut(value, ExpectedOut{Lines: map[int]string{2: "line 3"}})
 
 	assert.False(t, got.Success)
 	diff := `--- Got
 +++ Expected
 @@ -1 +1 @@
--
-+my
+-line 2
++line 3
 `
 	assert.Equal(t, diff, got.Diff)
 }
@@ -142,23 +156,6 @@ contains
 	assert.Equal(t, diff, got.Diff)
 }
 
-func Test_ValidateExpectedOut_PanicIfLineDoesNotExist_TooHigh(t *testing.T) {
-	defer func() {
-		r := recover()
-		if r != nil {
-			assert.Equal(t, "Invalid line number given 99", r)
-		}
-		assert.NotNil(t, r)
-	}()
-
-	value := `my
-multi
-line
-output`
-
-	_ = validateExpectedOut(value, ExpectedOut{Lines: map[int]string{99: "my"}})
-}
-
 func Test_ValidateExpectedOut_PanicIfLineDoesNotExist(t *testing.T) {
 	defer func() {
 		r := recover()