chore(context): test context initialization and handler logic (#4087)

* enhance code imported by #3413

if it needs to check if the handler is nil, tie c.index shall
always ++

* test: refactor test context initialization and handler logic

- Remove an empty line in `TestContextInitQueryCache`
- Add `TestContextNext` function with tests for `Next` method behavior with no handlers, one handler, and multiple handlers

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

---------

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Co-authored-by: zjj <zhong2plus@gmail.com>

context.go

@@ -186,10 +186,9 @@ func (c *Context) FullPath() string {
 func (c *Context) Next() {
 	c.index++
 	for c.index < int8(len(c.handlers)) {
-		if c.handlers[c.index] == nil {
-			continue
-		}
+		if c.handlers[c.index] != nil {
 			c.handlers[c.index](c)
+		}
 		c.index++
 	}
 }

context_test.go

@@ -610,7 +610,6 @@ func TestContextInitQueryCache(t *testing.T) {
 			assert.Equal(t, test.expectedQueryCache, test.testContext.queryCache)
 		})
 	}
-
 }
 
 func TestContextDefaultQueryOnEmptyRequest(t *testing.T) {
@@ -3038,3 +3037,47 @@ func TestInterceptedHeader(t *testing.T) {
 	assert.Equal(t, "", w.Result().Header.Get("X-Test"))
 	assert.Equal(t, "present", w.Result().Header.Get("X-Test-2"))
 }
+
+func TestContextNext(t *testing.T) {
+	c, _ := CreateTestContext(httptest.NewRecorder())
+
+	// Test with no handlers
+	c.Next()
+	assert.Equal(t, int8(0), c.index)
+
+	// Test with one handler
+	c.index = -1
+	c.handlers = HandlersChain{func(c *Context) {
+		c.Set("key", "value")
+	}}
+	c.Next()
+	assert.Equal(t, int8(1), c.index)
+	value, exists := c.Get("key")
+	assert.True(t, exists)
+	assert.Equal(t, "value", value)
+
+	// Test with multiple handlers
+	c.handlers = HandlersChain{
+		func(c *Context) {
+			c.Set("key1", "value1")
+			c.Next()
+			c.Set("key2", "value2")
+		},
+		nil,
+		func(c *Context) {
+			c.Set("key3", "value3")
+		},
+	}
+	c.index = -1
+	c.Next()
+	assert.Equal(t, int8(4), c.index)
+	value, exists = c.Get("key1")
+	assert.True(t, exists)
+	assert.Equal(t, "value1", value)
+	value, exists = c.Get("key2")
+	assert.True(t, exists)
+	assert.Equal(t, "value2", value)
+	value, exists = c.Get("key3")
+	assert.True(t, exists)
+	assert.Equal(t, "value3", value)
+}