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, 40 insertions, 0 deletions

diff --git a/internal/generate/format_test.go b/internal/generate/format_test.go
index f8f078b..a77ee2a 100644
--- a/internal/generate/format_test.go
+++ b/internal/generate/format_test.go
@@ -172,3 +172,43 @@ func TestParseFormatError(t *testing.T) {
 		t.Error("expected error for field without name")
 	}
 }
+
+func TestParseFormatEmptyInput(t *testing.T) {
+	formats, err := ParseFormats(strings.NewReader(""))
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(formats) != 0 {
+		t.Errorf("expected 0 formats, got %d", len(formats))
+	}
+}
+
+func TestParseFormatIDWithoutName(t *testing.T) {
+	_, err := ParseFormats(strings.NewReader("ID: 123\n"))
+	if err == nil {
+		t.Error("expected error for ID without preceding name")
+	}
+}
+
+func TestParseFormatInvalidID(t *testing.T) {
+	input := "name: sys_enter_test\nID: notanumber\n"
+	_, err := ParseFormats(strings.NewReader(input))
+	if err == nil {
+		t.Error("expected error for non-numeric ID")
+	}
+}
+
+func TestParseFieldNotEnoughParts(t *testing.T) {
+	input := "name: sys_enter_test\nID: 100\nfield:unsigned int fd;	offset:16\n"
+	_, err := ParseFormats(strings.NewReader(input))
+	if err == nil {
+		t.Error("expected error for field with fewer than 4 semicolons")
+	}
+}
+
+func TestSplitDeclarationEmpty(t *testing.T) {
+	typePart, namePart := splitDeclaration("")
+	if typePart != "" || namePart != "" {
+		t.Errorf("splitDeclaration(\"\") = (%q, %q), want (\"\", \"\")", typePart, namePart)
+	}
+}