coverage: add tests for interaction edge cases

[vbreuss]

This pull request significantly expands the unit test coverage for the FastBuffer and related classes, focusing on verifying the correct behavior of record boxing, caching, publishing, and event raising logic. The new tests ensure that internal optimizations (such as caching boxed interaction records) and event notification mechanisms are robust and not accidentally broken by future changes. Additionally, the tests pin correct behavior for consuming method buffers when empty, guarding against regressions.

The most important changes are:

Caching and Boxing Behavior Tests

• Added tests to verify that AppendBoxed and AppendBoxedUnverified methods on event and method buffers correctly cache and reuse boxed interaction records, preventing unnecessary allocations. These tests cover both event subscription/unsubscription and method invocation buffers of various arities.
• Added a test to ensure that AppendBoxedUnverified on an unsubscribe buffer boxes records as EventUnsubscription, not EventSubscription, pinning the correct conditional logic.

Event Publishing and Raising Tests

• Introduced a reusable helper and new tests to verify that AppendWithAccess on all indexer getter/setter buffer types publishes the interaction and raises the InteractionAdded event as expected, ensuring coverage for all indexer arities.

Buffer Consumption Edge Cases

• Added tests to verify that calling ConsumeAll on empty method buffers (for arities 1 through 4) returns zero and does not throw, pinning correct loop bounds and guarding against null reference exceptions.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
2 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Test Results

    21 files  ±  0      21 suites  ±0   9m 33s ⏱️ +38s
 3 928 tests + 45   3 926 ✅ + 45  2 💤 ±0  0 ❌ ±0 
25 514 runs  +315  25 510 ✅ +315  4 💤 ±0  0 ❌ ±0 

Results for commit 00490d1. ± Comparison against base commit ffa9d1c.

[github-actions]

🚀 Benchmark Results

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

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

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Event_Mockolate	372.7 ns	7.00 ns	6.54 ns	1.00	0.02	0.1254	0.0005	2.05 KB	1.00
Event_Moq	16,355.9 ns	76.78 ns	64.11 ns	43.90	0.76	0.7324	-	12.51 KB	6.09
Event_NSubstitute	5,942.4 ns	27.38 ns	22.87 ns	15.95	0.28	0.5493	0.0076	9.05 KB	4.40
Event_FakeItEasy	210,944.3 ns	671.02 ns	627.67 ns	566.20	9.68	0.7324	0.4883	15.39 KB	7.49
Event_Imposter	1,469.1 ns	24.48 ns	22.90 ns	3.94	0.09	0.5379	0.0153	8.8 KB	4.29
Event_TUnitMocks	203.0 ns	4.16 ns	3.89 ns	0.54	0.01	0.0837	0.0002	1.37 KB	0.67

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

AMD EPYC 9V74 2.60GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	N	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Indexer_Mockolate	1	1,060.6 ns	7.98 ns	6.66 ns	1.00	0.01	0.2460	0.0019	4.03 KB	1.00
Indexer_Moq	1	170,324.6 ns	945.21 ns	789.29 ns	160.59	1.21	0.9766	0.4883	20.45 KB	5.07
Indexer_NSubstitute	1	8,556.4 ns	99.23 ns	87.97 ns	8.07	0.09	0.7782	-	12.84 KB	3.18
Indexer_FakeItEasy	1	9,993.6 ns	162.44 ns	151.95 ns	9.42	0.15	0.8392	0.0305	13.88 KB	3.44
Indexer_Imposter	1	956.9 ns	14.95 ns	13.99 ns	0.90	0.01	0.3147	0.0038	5.16 KB	1.28
Indexer_Mockolate	10	2,628.1 ns	9.49 ns	8.41 ns	1.00	0.00	0.3090	-	5.09 KB	1.00
Indexer_Moq	10	184,606.5 ns	514.96 ns	481.69 ns	70.24	0.28	1.7090	1.4648	29.97 KB	5.89
Indexer_NSubstitute	10	20,797.9 ns	89.12 ns	69.58 ns	7.91	0.04	1.5564	0.0305	25.63 KB	5.04
Indexer_FakeItEasy	10	21,814.7 ns	279.61 ns	261.55 ns	8.30	0.10	2.1667	0.0610	35.47 KB	6.97
Indexer_Imposter	10	2,240.4 ns	24.52 ns	22.93 ns	0.85	0.01	0.4845	0.0076	7.97 KB	1.57

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

AMD EPYC 9V74 2.87GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	N	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Method_Mockolate	1	441.4 ns	2.42 ns	2.26 ns	1.00	0.01	0.1416	0.0010	2.32 KB	1.00
Method_Moq	1	126,548.8 ns	458.99 ns	383.28 ns	286.71	1.65	0.4883	-	14.58 KB	6.28
Method_NSubstitute	1	5,228.5 ns	14.56 ns	12.91 ns	11.85	0.07	0.5569	0.0076	9.12 KB	3.93
Method_FakeItEasy	1	5,275.8 ns	24.25 ns	22.69 ns	11.95	0.08	0.4959	-	8.11 KB	3.50
Method_Imposter	1	538.2 ns	2.13 ns	1.78 ns	1.22	0.01	0.2470	0.0029	4.04 KB	1.74
Method_TUnitMocks	1	692.6 ns	3.08 ns	2.40 ns	1.57	0.01	0.1774	0.0010	2.9 KB	1.25
Method_Mockolate	10	713.5 ns	2.84 ns	2.37 ns	1.00	0.00	0.1545	0.0010	2.53 KB	1.00
Method_Moq	10	132,042.3 ns	547.02 ns	511.69 ns	185.08	0.91	0.9766	0.7324	18.48 KB	7.30
Method_NSubstitute	10	7,797.9 ns	25.11 ns	23.49 ns	10.93	0.05	0.7324	0.0153	12.07 KB	4.77
Method_FakeItEasy	10	8,259.3 ns	30.01 ns	26.60 ns	11.58	0.05	0.9766	0.0305	16.05 KB	6.34
Method_Imposter	10	1,133.5 ns	4.86 ns	4.54 ns	1.59	0.01	0.3376	0.0057	5.52 KB	2.18
Method_TUnitMocks	10	1,773.7 ns	3.57 ns	3.16 ns	2.49	0.01	0.2747	0.0019	4.49 KB	1.77

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

Intel Xeon Platinum 8370C CPU 2.80GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v4
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	N	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Property_Mockolate	1	627.5 ns	22.49 ns	21.04 ns	1.00	0.05	0.1049	-	2.58 KB	1.00
Property_Moq	1	11,240.3 ns	25.15 ns	22.29 ns	17.93	0.59	0.3662	-	10.27 KB	3.98
Property_NSubstitute	1	7,521.3 ns	68.48 ns	64.06 ns	12.00	0.40	0.4654	0.0076	11.45 KB	4.44
Property_FakeItEasy	1	8,220.9 ns	83.84 ns	74.32 ns	13.11	0.44	0.4578	-	11.25 KB	4.36
Property_Imposter	1	489.3 ns	7.69 ns	7.19 ns	0.78	0.03	0.1268	0.0010	3.13 KB	1.21
Property_TUnitMocks	1	833.6 ns	7.97 ns	7.45 ns	1.33	0.04	0.1020	-	2.51 KB	0.97
Property_Mockolate	10	1,352.1 ns	13.77 ns	12.88 ns	1.00	0.01	0.1240	-	3.07 KB	1.00
Property_Moq	10	17,714.7 ns	68.21 ns	63.80 ns	13.10	0.13	0.6714	-	17.03 KB	5.55
Property_NSubstitute	10	16,843.0 ns	65.03 ns	60.83 ns	12.46	0.12	0.8545	-	21.08 KB	6.87
Property_FakeItEasy	10	18,895.3 ns	70.96 ns	62.90 ns	13.98	0.14	1.2512	0.0305	30.8 KB	10.03
Property_Imposter	10	1,393.9 ns	22.83 ns	21.35 ns	1.03	0.02	0.1888	0.0019	4.67 KB	1.52
Property_TUnitMocks	10	2,731.3 ns	5.01 ns	4.69 ns	2.02	0.02	0.1869	-	4.66 KB	1.52

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.4 LTS (Noble Numbat)

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

.NET SDK 10.0.203

[Host] : .NET 10.0.7 (10.0.7, 10.0.726.21808), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Callback_Mockolate	394.9 ns	9.58 ns	8.49 ns	1.00	0.03	0.1197	-	1.96 KB	1.00
Callback_Moq	95,332.5 ns	350.27 ns	327.64 ns	241.50	4.96	0.4883	0.2441	8.88 KB	4.53
Callback_NSubstitute	4,379.3 ns	13.01 ns	12.17 ns	11.09	0.23	0.4730	0.0076	7.74 KB	3.95
Callback_FakeItEasy	4,689.1 ns	40.38 ns	37.77 ns	11.88	0.26	0.4120	0.0153	6.81 KB	3.47
Callback_Imposter	403.3 ns	1.51 ns	1.34 ns	1.02	0.02	0.1454	0.0010	2.38 KB	1.22
Callback_TUnitMocks	609.7 ns	3.13 ns	2.61 ns	1.54	0.03	0.1602	0.0010	2.63 KB	1.34