coverage: add missing tests for Callback

[vbreuss]

This PR adds test coverage for the Callback class's For and When methods, particularly testing how they work together to limit the number of matching invocations. The changes include tests for both void and return methods, with and without InParallel, and new low-level unit tests for the Callback class itself.

Key Changes:

• Added tests for For method behavior when combined with When conditions in return method setups
• Added tests for For method behavior when combined with When conditions in void method setups and callbacks
• Created a new test file with direct unit tests for the Callback class

[Copilot]

Pull request overview

This PR adds test coverage for the Callback class's For and When methods, particularly testing how they work together to limit the number of matching invocations. The changes include tests for both void and return methods, with and without InParallel, and new low-level unit tests for the Callback class itself.

Changes:

• Added tests for For method behavior when combined with When conditions in return method setups
• Added tests for For method behavior when combined with When conditions in void method setups and callbacks
• Created a new test file with direct unit tests for the Callback class
• Removed an unnecessary blank line from the Callback class implementation

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.

File	Description
Tests/Mockolate.Tests/MockMethods/SetupMethodTests.ReturnsThrowsTests.cs	Added tests for For method limiting matches on return and void method setups
Tests/Mockolate.Tests/MockMethods/SetupMethodTests.CallbackTests.cs	Added tests for For method limiting matches on callbacks with and without InParallel
Tests/Mockolate.Internal.Tests/CallbackTests.cs	New file with direct unit tests for the Callback class's Invoke methods with For and When
Source/Mockolate/Setup/Callback.cs	Removed unnecessary blank line

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Test Results

    21 files  ±  0      21 suites  ±0   6m 6s ⏱️ +33s
 2 397 tests + 18   2 396 ✅ + 18  1 💤 ±0  0 ❌ ±0 
16 072 runs  +126  16 071 ✅ +126  1 💤 ±0  0 ❌ ±0 

Results for commit f756af9. ± Comparison against base commit 6ae56f2.

[github-actions]

🚀 Benchmark Results

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.3 LTS (Noble Numbat)

AMD EPYC 7763 2.45GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.102

[Host] : .NET 10.0.2 (10.0.2, 10.0.225.61305), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	Mean	Error	StdDev	Gen0	Gen1	Allocated
Simple_Mockolate	1.517 μs	0.0107 μs	0.0095 μs	0.2270	-	3.73 KB
Simple_Moq	179.803 μs	0.6038 μs	0.5042 μs	0.4883	-	14.77 KB
Simple_NSubstitute	5.642 μs	0.0191 μs	0.0179 μs	0.5569	0.0076	9.14 KB
Simple_FakeItEasy	6.225 μs	0.0213 μs	0.0189 μs	0.4959	-	8.11 KB

[github-actions]

This is addressed in release v1.0.3.