refactor(variants): extract ResolveBranch helper and consolidate test utilities

- Extract duplicated branch-resolution logic into a private ResolveBranch()
  method in both Entry and Query, eliminating inline ternary repetition
- Add DefaultBranch = "main" constant shared across Variant overloads
- Promote Query._Headers to internal visibility to remove reflection in unit tests
- Introduce UnitTestHelpers.GetMockClient() shared helper, removing duplicate
  private factory methods from EntryUnitTests and QueryUnitTests
- Strengthen integration test assertions: use ThrowsAnyAsync and assert that
  exception message contains "branch" rather than just checking non-null
- Replace hard-coded "development" branch strings with TestDataHelper.BranchUid
- Bump contentstack.utils dependency from 2.0.0 to 2.0.1

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: OMpawar-21

Contentstack.Core.Tests/Integration/VariantsTests/EntryVariantsComprehensiveTest.cs

@@ -39,7 +39,7 @@ public async Task Variant_WithInvalidBranch_ThrowsException()
             // Act & Assert
             LogAct("Fetching entry with variant and INVALID branch using .Variant() method");
 
-            var exception = await Assert.ThrowsAsync<Exception>(async () => 
+            var exception = await Assert.ThrowsAnyAsync<Exception>(async () => 
             {
                 await client
                     .ContentType(TestDataHelper.ComplexContentTypeUid)
@@ -48,8 +48,8 @@ await client
                     .Fetch<Entry>();
             });
 
-            LogAssert("Verifying exception was thrown");
-            TestAssert.NotNull(exception);
+            LogAssert("Verifying exception was thrown for invalid branch");
+            Assert.Contains("branch", exception.Message, System.StringComparison.OrdinalIgnoreCase);
         }
 
         [Fact(DisplayName = "Entry Operations - Variant With Valid Branch Returns Results")]
@@ -60,7 +60,7 @@ public async Task Variant_WithValidBranch_ReturnsResults()
             LogContext("ContentType", TestDataHelper.ComplexContentTypeUid);
             LogContext("EntryUid", TestDataHelper.ComplexEntryUid);
             LogContext("VariantUid", TestDataHelper.VariantUid);
-            LogContext("Branch", "development");
+            LogContext("Branch", TestDataHelper.BranchUid);
 
             var client = CreateClient();
 
@@ -70,7 +70,7 @@ public async Task Variant_WithValidBranch_ReturnsResults()
             var entry = await client
                 .ContentType(TestDataHelper.ComplexContentTypeUid)
                 .Entry(TestDataHelper.ComplexEntryUid)
-                .Variant(TestDataHelper.VariantUid, "development")
+                .Variant(TestDataHelper.VariantUid, TestDataHelper.BranchUid)
                 .Fetch<Entry>();
 
             // Assert
@@ -329,13 +329,13 @@ public async Task Variant_Query_WithInvalidBranch_ThrowsException()
             query.Variant(TestDataHelper.VariantUid, "invalid_branch_name_123");
             query.Limit(5);
 
-            var exception = await Assert.ThrowsAsync<Exception>(async () => 
+            var exception = await Assert.ThrowsAnyAsync<Exception>(async () => 
             {
                 await query.Find<Entry>();
             });
 
-            LogAssert("Verifying exception was thrown");
-            TestAssert.NotNull(exception);
+            LogAssert("Verifying exception was thrown for invalid branch");
+            Assert.Contains("branch", exception.Message, System.StringComparison.OrdinalIgnoreCase);
         }
 
         [Fact(DisplayName = "Entry Operations - Variant Query With Valid Branch Returns Results")]
@@ -345,15 +345,15 @@ public async Task Variant_Query_WithValidBranch_ReturnsResults()
             LogArrange("Setting up query operation with valid branch");
             LogContext("ContentType", TestDataHelper.ComplexContentTypeUid);
             LogContext("VariantUid", TestDataHelper.VariantUid);
-            LogContext("Branch", "development");
+            LogContext("Branch", TestDataHelper.BranchUid);
 
             var client = CreateClient();
             var query = client.ContentType(TestDataHelper.ComplexContentTypeUid).Query();
 
             // Act
             LogAct("Executing query with variant and valid branch");
 
-            query.Variant(TestDataHelper.VariantUid, "development");
+            query.Variant(TestDataHelper.VariantUid, TestDataHelper.BranchUid);
             query.Limit(5);
             var result = await query.Find<Entry>();
 

Contentstack.Core.Unit.Tests/EntryUnitTests.cs

@@ -2748,32 +2748,20 @@ public void Entry_Fetch_WithCachePolicyNotSet_Setup_VerifiesDefault()
 
         #region Variant Tests
 
-        private ContentstackClient GetMockClient(string stackBranch = null)
-        {
-            var options = new ContentstackOptions
-            {
-                ApiKey = "dummy_api_key",
-                DeliveryToken = "dummy_delivery_token",
-                Environment = "dummy_environment",
-                Branch = stackBranch
-            };
-            return new ContentstackClient(options);
-        }
-
         [Fact(DisplayName = "Entry Operations - Variant With Branch Sets Branch Header")]
         public void Entry_Variant_WithBranch_SetsBranchHeader()
         {
             // Arrange
-            var client = GetMockClient("main");
-            var entry = client.ContentType("dummy_content_type").Entry("dummy_entry_uid");
+            var client = UnitTestHelpers.GetMockClient("main");
+            var entry = client.ContentType("DUMMY_CONTENT_TYPE").Entry("DUMMY_ENTRY_UID");
 
             // Act
-            entry.Variant("variant_1", "development");
+            entry.Variant("VARIANT_1", "development");
 
             // Assert
             Assert.True(entry._Headers.ContainsKey("x-cs-variant-uid"));
-            Assert.Equal("variant_1", entry._Headers["x-cs-variant-uid"]);
-            
+            Assert.Equal("VARIANT_1", entry._Headers["x-cs-variant-uid"]);
+
             Assert.True(entry._Headers.ContainsKey("branch"));
             Assert.Equal("development", entry._Headers["branch"]);
         }
@@ -2782,16 +2770,16 @@ public void Entry_Variant_WithBranch_SetsBranchHeader()
         public void Entry_Variant_WithNullBranch_FallsBackToStackBranch()
         {
             // Arrange
-            var client = GetMockClient("stack_branch");
-            var entry = client.ContentType("dummy_content_type").Entry("dummy_entry_uid");
+            var client = UnitTestHelpers.GetMockClient("stack_branch");
+            var entry = client.ContentType("DUMMY_CONTENT_TYPE").Entry("DUMMY_ENTRY_UID");
 
             // Act
-            entry.Variant("variant_1", null);
+            entry.Variant("VARIANT_1", null);
 
             // Assert
             Assert.True(entry._Headers.ContainsKey("x-cs-variant-uid"));
-            Assert.Equal("variant_1", entry._Headers["x-cs-variant-uid"]);
-            
+            Assert.Equal("VARIANT_1", entry._Headers["x-cs-variant-uid"]);
+
             Assert.True(entry._Headers.ContainsKey("branch"));
             Assert.Equal("stack_branch", entry._Headers["branch"]);
         }
@@ -2800,16 +2788,16 @@ public void Entry_Variant_WithNullBranch_FallsBackToStackBranch()
         public void Entry_Variant_WithEmptyBranch_FallsBackToMainIfStackBranchIsNull()
         {
             // Arrange
-            var client = GetMockClient(null);
-            var entry = client.ContentType("dummy_content_type").Entry("dummy_entry_uid");
+            var client = UnitTestHelpers.GetMockClient(null);
+            var entry = client.ContentType("DUMMY_CONTENT_TYPE").Entry("DUMMY_ENTRY_UID");
 
             // Act
-            entry.Variant("variant_1", "   ");
+            entry.Variant("VARIANT_1", "   ");
 
             // Assert
             Assert.True(entry._Headers.ContainsKey("x-cs-variant-uid"));
-            Assert.Equal("variant_1", entry._Headers["x-cs-variant-uid"]);
-            
+            Assert.Equal("VARIANT_1", entry._Headers["x-cs-variant-uid"]);
+
             Assert.True(entry._Headers.ContainsKey("branch"));
             Assert.Equal("main", entry._Headers["branch"]);
         }
@@ -2818,17 +2806,17 @@ public void Entry_Variant_WithEmptyBranch_FallsBackToMainIfStackBranchIsNull()
         public void Entry_Variant_WithMultipleVariantsAndBranch_SetsHeaders()
         {
             // Arrange
-            var client = GetMockClient("main");
-            var entry = client.ContentType("dummy_content_type").Entry("dummy_entry_uid");
-            var variants = new List<string> { "variant_1", "variant_2" };
+            var client = UnitTestHelpers.GetMockClient("main");
+            var entry = client.ContentType("DUMMY_CONTENT_TYPE").Entry("DUMMY_ENTRY_UID");
+            var variants = new List<string> { "VARIANT_1", "VARIANT_2" };
 
             // Act
             entry.Variant(variants, "feature_branch");
 
             // Assert
             Assert.True(entry._Headers.ContainsKey("x-cs-variant-uid"));
-            Assert.Equal("variant_1,variant_2", entry._Headers["x-cs-variant-uid"]);
-            
+            Assert.Equal("VARIANT_1,VARIANT_2", entry._Headers["x-cs-variant-uid"]);
+
             Assert.True(entry._Headers.ContainsKey("branch"));
             Assert.Equal("feature_branch", entry._Headers["branch"]);
         }

Contentstack.Core.Unit.Tests/QueryUnitTests.cs

@@ -2635,101 +2635,69 @@ public void Query_WithNullUrlQueries_Setup_HandlesGracefully()
 
         #region Variant Tests
 
-        private ContentstackClient GetMockClient(string stackBranch = null)
-        {
-            var options = new ContentstackOptions
-            {
-                ApiKey = "dummy_api_key",
-                DeliveryToken = "dummy_delivery_token",
-                Environment = "dummy_environment",
-                Branch = stackBranch
-            };
-            return new ContentstackClient(options);
-        }
-
         [Fact(DisplayName = "Query Operations - Variant With Branch Sets Branch Header")]
         public void Query_Variant_WithBranch_SetsBranchHeader()
         {
             // Arrange
-            var client = GetMockClient("main");
-            var query = client.ContentType("dummy_content_type").Query();
+            var query = UnitTestHelpers.GetMockClient("main").ContentType("DUMMY_CONTENT_TYPE").Query();
 
             // Act
-            query.Variant("variant_1", "development");
+            query.Variant("VARIANT_1", "development");
 
             // Assert
-            var headersField = typeof(Query).GetField("_Headers", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
-            var headers = (Dictionary<string, object>)headersField.GetValue(query);
-            
-            Assert.True(headers.ContainsKey("x-cs-variant-uid"));
-            Assert.Equal("variant_1", headers["x-cs-variant-uid"]);
-            
-            Assert.True(headers.ContainsKey("branch"));
-            Assert.Equal("development", headers["branch"]);
+            Assert.True(query._Headers.ContainsKey("x-cs-variant-uid"));
+            Assert.Equal("VARIANT_1", query._Headers["x-cs-variant-uid"]);
+            Assert.True(query._Headers.ContainsKey("branch"));
+            Assert.Equal("development", query._Headers["branch"]);
         }
 
         [Fact(DisplayName = "Query Operations - Variant With Null Branch Falls Back To Stack Branch")]
         public void Query_Variant_WithNullBranch_FallsBackToStackBranch()
         {
             // Arrange
-            var client = GetMockClient("stack_branch");
-            var query = client.ContentType("dummy_content_type").Query();
+            var query = UnitTestHelpers.GetMockClient("stack_branch").ContentType("DUMMY_CONTENT_TYPE").Query();
 
             // Act
-            query.Variant("variant_1", null);
+            query.Variant("VARIANT_1", null);
 
             // Assert
-            var headersField = typeof(Query).GetField("_Headers", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
-            var headers = (Dictionary<string, object>)headersField.GetValue(query);
-
-            Assert.True(headers.ContainsKey("x-cs-variant-uid"));
-            Assert.Equal("variant_1", headers["x-cs-variant-uid"]);
-            
-            Assert.True(headers.ContainsKey("branch"));
-            Assert.Equal("stack_branch", headers["branch"]);
+            Assert.True(query._Headers.ContainsKey("x-cs-variant-uid"));
+            Assert.Equal("VARIANT_1", query._Headers["x-cs-variant-uid"]);
+            Assert.True(query._Headers.ContainsKey("branch"));
+            Assert.Equal("stack_branch", query._Headers["branch"]);
         }
 
         [Fact(DisplayName = "Query Operations - Variant With Empty Branch Falls Back To Main If Stack Branch Is Null")]
         public void Query_Variant_WithEmptyBranch_FallsBackToMainIfStackBranchIsNull()
         {
             // Arrange
-            var client = GetMockClient(null);
-            var query = client.ContentType("dummy_content_type").Query();
+            var query = UnitTestHelpers.GetMockClient(null).ContentType("DUMMY_CONTENT_TYPE").Query();
 
             // Act
-            query.Variant("variant_1", "   ");
+            query.Variant("VARIANT_1", "   ");
 
             // Assert
-            var headersField = typeof(Query).GetField("_Headers", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
-            var headers = (Dictionary<string, object>)headersField.GetValue(query);
-
-            Assert.True(headers.ContainsKey("x-cs-variant-uid"));
-            Assert.Equal("variant_1", headers["x-cs-variant-uid"]);
-            
-            Assert.True(headers.ContainsKey("branch"));
-            Assert.Equal("main", headers["branch"]);
+            Assert.True(query._Headers.ContainsKey("x-cs-variant-uid"));
+            Assert.Equal("VARIANT_1", query._Headers["x-cs-variant-uid"]);
+            Assert.True(query._Headers.ContainsKey("branch"));
+            Assert.Equal("main", query._Headers["branch"]);
         }
 
         [Fact(DisplayName = "Query Operations - Variant With Multiple Variants And Branch Sets Headers")]
         public void Query_Variant_WithMultipleVariantsAndBranch_SetsHeaders()
         {
             // Arrange
-            var client = GetMockClient("main");
-            var query = client.ContentType("dummy_content_type").Query();
-            var variants = new List<string> { "variant_1", "variant_2" };
+            var query = UnitTestHelpers.GetMockClient("main").ContentType("DUMMY_CONTENT_TYPE").Query();
+            var variants = new List<string> { "VARIANT_1", "VARIANT_2" };
 
             // Act
             query.Variant(variants, "feature_branch");
 
             // Assert
-            var headersField = typeof(Query).GetField("_Headers", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
-            var headers = (Dictionary<string, object>)headersField.GetValue(query);
-
-            Assert.True(headers.ContainsKey("x-cs-variant-uid"));
-            Assert.Equal("variant_1,variant_2", headers["x-cs-variant-uid"]);
-            
-            Assert.True(headers.ContainsKey("branch"));
-            Assert.Equal("feature_branch", headers["branch"]);
+            Assert.True(query._Headers.ContainsKey("x-cs-variant-uid"));
+            Assert.Equal("VARIANT_1,VARIANT_2", query._Headers["x-cs-variant-uid"]);
+            Assert.True(query._Headers.ContainsKey("branch"));
+            Assert.Equal("feature_branch", query._Headers["branch"]);
         }
 
         #endregion

Contentstack.Core.Unit.Tests/UnitTestHelpers.cs

@@ -0,0 +1,20 @@
+using Contentstack.Core;
+using Contentstack.Core.Configuration;
+
+namespace Contentstack.Core.Unit.Tests
+{
+    internal static class UnitTestHelpers
+    {
+        internal static ContentstackClient GetMockClient(string stackBranch = null)
+        {
+            var options = new ContentstackOptions
+            {
+                ApiKey = "DUMMY_API_KEY",
+                DeliveryToken = "DUMMY_DELIVERY_TOKEN",
+                Environment = "DUMMY_ENVIRONMENT",
+                Branch = stackBranch
+            };
+            return new ContentstackClient(options);
+        }
+    }
+}

Contentstack.Core/Contentstack.Core.csproj

@@ -32,7 +32,7 @@
     <PackageReference Include="System.Text.Json" Version="8.0.5" />
     <PackageReference Include="Microsoft.Extensions.Options" Version="8.0.2" />
     <PackageReference Include="Markdig" Version="0.36.2" />
-    <PackageReference Include="contentstack.utils" Version="2.0.0" />
+    <PackageReference Include="contentstack.utils" Version="2.0.1" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" Condition="'$(TargetFramework)' == 'net47' Or '$(TargetFramework)' == 'net472'" />
   </ItemGroup>
   <ItemGroup>

Contentstack.Core/Models/Entry.cs

@@ -395,12 +395,13 @@ public void RemoveHeader(string key)
         /// To set variants header using Entry instance.
         /// </summary>
         /// <param name="variant_header">Entry instance</param>
+        /// <param name="branch">Optional branch to fetch the variant from. Falls back to the stack's configured branch, then "main".</param>
         /// <returns>Current instance of Entry, this will be useful for a chaining calls.</returns>
         /// <example>
         /// <code>
         ///     ContentstackClient stack = new ContentstackClinet("api_key", "delivery_token", "environment");
         ///     Entry csEntry = stack.ContentType("contentType_id").Entry("entry_uid");
-        ///     
+        ///
         ///     csEntry.Variant("variant_entry_1");
         ///     csEntry.Fetch<Product>().ContinueWith((entryResult) => {
         ///         //Your callback code.
@@ -411,10 +412,7 @@ public void RemoveHeader(string key)
         public Entry Variant(string variant_header, string branch = null)
         {
             this.SetHeader("x-cs-variant-uid", variant_header);
-            string branchToUse = string.IsNullOrWhiteSpace(branch) 
-                ? (this.ContentTypeInstance?.StackInstance?.Config?.Branch ?? "main") 
-                : branch;
-            this.SetHeader("branch", branchToUse);
+            this.SetHeader("branch", ResolveBranch(branch));
             return this;
         }
 
@@ -424,12 +422,13 @@ public Entry Variant(string variant_header, string branch = null)
         /// To set multiple variants headers using Entry instance.
         /// </summary>
         /// <param name="variant_headers">Entry instance</param>
+        /// <param name="branch">Optional branch to fetch the variant from. Falls back to the stack's configured branch, then "main".</param>
         /// <returns>Current instance of Entry, this will be useful for a chaining calls.</returns>
         /// <example>
         /// <code>
         ///     ContentstackClient stack = new ContentstackClinet("api_key", "delivery_token", "environment");
         ///     Entry csEntry = stack.ContentType("contentType_id").Query();
-        ///     
+        ///
         ///     csEntry.Variant(new List<string> { "variant_entry_1", "variant_entry_2", "variant_entry_3" });
         ///     csEntry.Fetch<Product>().ContinueWith((entryResult) => {
         ///         //Your callback code.
@@ -440,13 +439,17 @@ public Entry Variant(string variant_header, string branch = null)
         public Entry Variant(List<string> variant_headers, string branch = null)
         {
             this.SetHeader("x-cs-variant-uid", string.Join(",", variant_headers));
-            string branchToUse = string.IsNullOrWhiteSpace(branch) 
-                ? (this.ContentTypeInstance?.StackInstance?.Config?.Branch ?? "main") 
-                : branch;
-            this.SetHeader("branch", branchToUse);
+            this.SetHeader("branch", ResolveBranch(branch));
             return this;
         }
 
+        private const string DefaultBranch = "main";
+
+        private string ResolveBranch(string branch) =>
+            string.IsNullOrWhiteSpace(branch)
+                ? (ContentTypeInstance?.StackInstance?.Config?.Branch ?? DefaultBranch)
+                : branch;
+
         /// <summary>
         /// Get metadata of entry.
         /// </summary>