Add unit tests for GlobalFieldsResultCallback, verifying onCompletion and always methods to ensure correct behavior and enhance test coverage.

Author: harshithad0703

contentstack/src/test/java/com/contentstack/sdk/TestGlobalFieldsResultCallback.java

@@ -0,0 +1,67 @@
+package com.contentstack.sdk;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class TestGlobalFieldsResultCallback {
+
+    private static class TestGlobalFieldsCallback extends GlobalFieldsResultCallback {
+
+        GlobalFieldsModel lastModel;
+        Error lastError;
+        boolean onCompletionCalled = false;
+        boolean alwaysCalled = false;
+
+        @Override
+        public void onCompletion(GlobalFieldsModel globalFieldsModel, Error error) {
+            onCompletionCalled = true;
+            lastModel = globalFieldsModel;
+            lastError = error;
+        }
+
+        @Override
+        void always() {
+            alwaysCalled = true;
+        }
+    }
+
+    @Test
+    public void testOnRequestFinishCallsOnCompletionWithModelAndNullError() {
+        TestGlobalFieldsCallback callback = new TestGlobalFieldsCallback();
+
+        // we don't need a real GlobalFieldsModel, just a non-null reference;
+        // but if it's hard to construct, we can pass null and test behavior.
+        GlobalFieldsModel model = null;
+
+        callback.onRequestFinish(model);
+
+        assertTrue(callback.onCompletionCalled);
+        assertEquals(model, callback.lastModel);
+        assertNull(callback.lastError);
+        assertFalse(callback.alwaysCalled);
+    }
+
+    @Test
+    public void testOnRequestFailCallsOnCompletionWithErrorAndNullModel() {
+        TestGlobalFieldsCallback callback = new TestGlobalFieldsCallback();
+
+        Error error = new Error(); // your SDK Error (no-arg ctor)
+
+        callback.onRequestFail(ResponseType.NETWORK, error); // use any valid ResponseType
+
+        assertTrue(callback.onCompletionCalled);
+        assertNull(callback.lastModel);
+        assertEquals(error, callback.lastError);
+        assertFalse(callback.alwaysCalled);
+    }
+
+    @Test
+    public void testAlwaysOverrideIsCallable() {
+        TestGlobalFieldsCallback callback = new TestGlobalFieldsCallback();
+
+        callback.always();
+
+        assertTrue(callback.alwaysCalled);
+    }
+}