Add unit test for header provider

internal/provider/header_test.go

@@ -0,0 +1,32 @@
+package provider
+
+import (
+	"context"
+	"net/http"
+	"testing"
+)
+
+func TestCustomHeaderIntercept(t *testing.T) {
+	expectedName := "X-Custom-Header"
+	expectedValue := "Custom-Value"
+	header := NewHeaderProvider(expectedName, expectedValue)
+
+	req, err := http.NewRequest("GET", "https://example.com", nil)
+	if err != nil {
+		t.Fatalf("Failed to create HTTP request: %v", err)
+	}
+
+	ctx := context.Background()
+
+	// Call the Intercept method (method being tested)
+	err = header.Intercept(ctx, req)
+	if err != nil {
+		t.Errorf("Intercept failed: %v", err)
+	}
+
+	// Verify that the custom header is set correctly
+	if req.Header.Get(expectedName) != expectedValue {
+		t.Errorf("Expected header '%s' to have value '%s', got '%s'", expectedName, expectedValue,
+			req.Header.Get(expectedName))
+	}
+}