diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..f945433
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,72 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"reflect"
+	"runtime"
+	"testing"
+)
+
+func TestGetIgnoreList(t *testing.T) {
+	tmpFile, err := os.CreateTemp("", "gptignore")
+	if err != nil {
+		t.Fatalf("failed to create temp file: %v", err)
+	}
+	defer os.Remove(tmpFile.Name())
+
+	content := "# comment\nlogs/\n\nassets/*.min.js\n"
+	if _, err := tmpFile.WriteString(content); err != nil {
+		t.Fatalf("failed to write temp file: %v", err)
+	}
+	tmpFile.Close()
+
+	list, err := getIgnoreList(tmpFile.Name())
+	if err != nil {
+		t.Fatalf("getIgnoreList returned error: %v", err)
+	}
+
+	expected := []string{"logs/**", "assets/*.min.js"}
+	if runtime.GOOS == "windows" {
+		expected = []string{"logs\\**", "assets\\*.min.js"}
+	}
+	if !reflect.DeepEqual(list, expected) {
+		t.Fatalf("expected %v, got %v", expected, list)
+	}
+}
+
+func TestShouldIgnore_DefaultAndNested(t *testing.T) {
+	cases := []struct {
+		path string
+		want bool
+	}{
+		{"node_modules", true},
+		{filepath.Join("node_modules", "pkg", "index.js"), true},
+		{filepath.Join("src", "node_modules", "index.js"), false},
+	}
+
+	for _, c := range cases {
+		if got := shouldIgnore(c.path, nil); got != c.want {
+			t.Errorf("shouldIgnore(%q) = %v, want %v", c.path, got, c.want)
+		}
+	}
+}
+
+func TestShouldIgnore_WithPatterns(t *testing.T) {
+	ignoreList := []string{"logs/**", "**/*.min.js", "docs/**/ignored/**"}
+	cases := []struct {
+		path string
+		want bool
+	}{
+		{filepath.Join("logs", "app.log"), true},
+		{filepath.Join("static", "js", "file.min.js"), true},
+		{filepath.Join("docs", "api", "ignored", "readme.md"), true},
+		{filepath.Join("docs", "api", "readme.md"), false},
+	}
+
+	for _, c := range cases {
+		if got := shouldIgnore(c.path, ignoreList); got != c.want {
+			t.Errorf("shouldIgnore(%q) = %v, want %v", c.path, got, c.want)
+		}
+	}
+}