Add more test coverage and improve error message

pprof/parser.go

@@ -198,7 +198,7 @@ func (p *rawParser) addSample(line string) {
 	funcIDs := p.parseFuncIDs(lineParts[1])
 
 	if len(samples) != len(p.columns) {
-		p.setError(fmt.Errorf("line has more samples (%v) than columns (%v): %v",
+		p.setError(fmt.Errorf("line has a different sample count (%v) than columns (%v): %v",
 			len(samples), len(p.columns), line))
 		return
 	}

pprof/parser_test.go

@@ -27,6 +27,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 	"github.com/uber/go-torch/stack"
 )
 
@@ -56,6 +57,8 @@ func TestParseMemProfile(t *testing.T) {
 func TestParse(t *testing.T) {
 	_, parser := parseTest1(t)
 
+	assert.Equal(t, []string{"samples/count", "cpu/nanoseconds"}, parser.columns)
+
 	// line 7 - 249 are stack records in the test file.
 	const expectedNumRecords = 242
 	if len(parser.records) != expectedNumRecords {
@@ -160,6 +163,18 @@ func TestParseMissingSourceLine(t *testing.T) {
 	}
 }
 
+func TestParseSampleCountMismatch(t *testing.T) {
+	contents := `Samples:
+	samples/count cpu/nanoseconds alloc_objects/count
+	   2   10000000: 1
+	Locations:
+	   1: 0xaaaaa funcName :0 s=0
+`
+	_, err := ParseRaw([]byte(contents))
+	require.Error(t, err, "Expected parseRaw to fail with sample count mismatch")
+	assert.Contains(t, err.Error(), "different sample count (2) than columns (3)")
+}
+
 func testParseRawBad(t *testing.T, errorReason, errorSubstr, contents string) {
 	_, err := ParseRaw([]byte(contents))
 	if err == nil {