Add negative tests for all internal unit tests (task 348)

- internal/types: Fix StringValue panic with no null terminator,
  add negative tests for serialization, Equals, and StringValue edge cases
- internal/file: Add negative tests for empty name, unknown flags,
  SetFlags/AddFlags, Dup, empty OldnameNewname and Pathname
- internal/flamegraph: Add negative tests for StringByName unknown field,
  Counter.ValueByName panic, merge empty, deserialize invalid data,
  serialize/deserialize round-trip
- internal/generate/format: Add negative tests for empty input, ID errors,
  malformed fields, empty declarations
- internal/generate/typesgo: Add negative tests for snakeToCamel edge cases,
  unknown types, invalid member/define parsing, no-import case
- internal/generate/tracepointsgo: Add negative tests for malformed SEC,
  no SEC lines
- internal/generate/codegen: Add negative tests for unknown event kind,
  invalid syscall grouping, missing exit tracepoint
- internal/generate/classify: Add negative tests for empty external fields,
  non-fd types

Amp-Thread-ID: https://ampcode.com/threads/T-019c81bf-3d5c-7216-b1b6-890db1374414
Co-authored-by: Amp <amp@ampcode.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/internal/generate/codegen_test.go b/internal/generate/codegen_test.go
index 23ab7c1..6402214 100644
--- a/internal/generate/codegen_test.go
+++ b/internal/generate/codegen_test.go
@@ -285,6 +285,41 @@ func TestEnterReject(t *testing.T) {
 	}
 }
 
+func TestEventStructNameUnknown(t *testing.T) {
+	if got := eventStructName(TracepointKind(999)); got != "unknown_event" {
+		t.Errorf("eventStructName(999) = %q, want \"unknown_event\"", got)
+	}
+}
+
+func TestEventTypeConstantUnknown(t *testing.T) {
+	if got := eventTypeConstant(TracepointKind(999), true); got != "ENTER_UNKNOWN_EVENT" {
+		t.Errorf("eventTypeConstant(999, true) = %q, want \"ENTER_UNKNOWN_EVENT\"", got)
+	}
+	if got := eventTypeConstant(TracepointKind(999), false); got != "EXIT_UNKNOWN_EVENT" {
+		t.Errorf("eventTypeConstant(999, false) = %q, want \"EXIT_UNKNOWN_EVENT\"", got)
+	}
+}
+
+func TestGroupBySyscallInvalid(t *testing.T) {
+	formats := []Format{
+		{Name: "tooshort", ID: 1},
+		{Name: "also_short", ID: 2},
+	}
+	output := GenerateTracepointsC(formats)
+	if strings.Contains(output, "SEC(") {
+		t.Error("formats with fewer than 3 name parts should not produce SEC handlers")
+	}
+}
+
+func TestClassifySyscallNoExit(t *testing.T) {
+	formats := mustParseAll(t, FormatRead)
+	output := GenerateTracepointsC(formats)
+	requireContains(t, output, "Ignoring")
+	if strings.Contains(output, "SEC(") {
+		t.Error("syscall with only enter and no exit should be ignored")
+	}
+}
+
 func requireContains(t *testing.T, haystack, needle string) {
 	t.Helper()
 	if !strings.Contains(haystack, needle) {