test: increase coverage to 98.9% by covering previously untested code paths

- ginS: add TestLoadHTMLGlob, TestLoadHTMLFiles, TestLoadHTMLFS covering the
  three HTML template loader wrappers (73.1% -> 100%)
- ginS: add TestRunError, TestRunTLSError, TestRunUnixError, TestRunFdError
  covering all four server-start wrappers via fast-failing error paths
- binding: add TestPlainBindingBody covering plainBinding.BindBody (string,
  []byte, unsupported type, and nil receiver branches)
- render: add TestRedirectWriteContentType covering the Redirect no-op method

Overall project coverage: 98.5% -> 98.9%
Patch coverage: 100%

binding/binding_test.go

@@ -1432,3 +1432,23 @@ func requestWithBody(method, path, body string) (req *http.Request) {
 	req, _ = http.NewRequest(method, path, bytes.NewBufferString(body))
 	return
 }
+
+func TestPlainBindingBody(t *testing.T) {
+	p := Plain
+
+	var s string
+	require.NoError(t, p.BindBody([]byte("hello body"), &s))
+	assert.Equal(t, "hello body", s)
+
+	var bs []byte
+	require.NoError(t, p.BindBody([]byte("bytes body"), &bs))
+	assert.Equal(t, []byte("bytes body"), bs)
+
+	var i int
+	require.Error(t, p.BindBody([]byte("fail"), &i))
+
+	require.NoError(t, p.BindBody([]byte(""), nil))
+
+	var ptr *string
+	require.NoError(t, p.BindBody([]byte(""), ptr))
+}

ginS/gins_test.go

@@ -244,3 +244,44 @@ func TestStaticFS(t *testing.T) {
 
 	assert.Equal(t, http.StatusOK, w.Code)
 }
+
+func TestLoadHTMLGlob(t *testing.T) {
+	assert.NotPanics(t, func() {
+		LoadHTMLGlob("../testdata/template/*.tmpl")
+	})
+	assert.NotNil(t, engine())
+}
+
+func TestLoadHTMLFiles(t *testing.T) {
+	assert.NotPanics(t, func() {
+		LoadHTMLFiles("../testdata/template/hello.tmpl", "../testdata/template/raw.tmpl")
+	})
+	assert.NotNil(t, engine())
+}
+
+func TestLoadHTMLFS(t *testing.T) {
+	assert.NotPanics(t, func() {
+		LoadHTMLFS(http.Dir("../testdata/template"), "*.tmpl")
+	})
+	assert.NotNil(t, engine())
+}
+
+func TestRunError(t *testing.T) {
+	err := Run("not-valid-address")
+	assert.Error(t, err)
+}
+
+func TestRunTLSError(t *testing.T) {
+	err := RunTLS(":0", "/nonexistent.cert", "/nonexistent.key")
+	assert.Error(t, err)
+}
+
+func TestRunUnixError(t *testing.T) {
+	err := RunUnix("/nonexistent/deep/path/gin-test.sock")
+	assert.Error(t, err)
+}
+
+func TestRunFdError(t *testing.T) {
+	err := RunFd(99999)
+	assert.Error(t, err)
+}

render/render_test.go

@@ -805,3 +805,14 @@ func TestRenderWriteError(t *testing.T) {
 	require.Error(t, err)
 	assert.Equal(t, "write error", err.Error())
 }
+
+func TestRedirectWriteContentType(t *testing.T) {
+	w := httptest.NewRecorder()
+	req, _ := http.NewRequest(http.MethodGet, "/", nil)
+	r := Redirect{Code: http.StatusFound, Request: req, Location: "/new"}
+	// WriteContentType is a no-op for Redirect; verify it doesn't panic
+	assert.NotPanics(t, func() {
+		r.WriteContentType(w)
+	})
+	assert.Empty(t, w.Header().Get("Content-Type"))
+}