Allow specifying context in AD testing

[penelopeysm]

This is necessary for TuringLang/Turing.jl#2307 because AD in sampling is run with a SamplingContext, not a DefaultContext. Thus to properly test AD there we need to be able to specify a context.

[github-actions]

Benchmark Report for Commit 73ed741

Computer Information

Julia Version 1.11.5
Commit 760b2e5b739 (2025-04-14 06:53 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 7763 64-Core Processor
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, znver3)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)

Benchmark Results

|                 Model | Dimension |  AD Backend |      VarInfo Type | Linked | Eval Time / Ref Time | AD Time / Eval Time |
|-----------------------|-----------|-------------|-------------------|--------|----------------------|---------------------|
| Simple assume observe |         1 | forwarddiff |             typed |  false |                  9.8 |                 1.5 |
|           Smorgasbord |       201 | forwarddiff |             typed |  false |                708.7 |                37.6 |
|           Smorgasbord |       201 | forwarddiff | simple_namedtuple |   true |                415.6 |                44.3 |
|           Smorgasbord |       201 | forwarddiff |           untyped |   true |               1208.9 |                27.1 |
|           Smorgasbord |       201 | forwarddiff |       simple_dict |   true |               3267.4 |                23.5 |
|           Smorgasbord |       201 | reversediff |             typed |   true |               1423.1 |                29.7 |
|           Smorgasbord |       201 |    mooncake |             typed |   true |                937.2 |                 5.3 |
|    Loop univariate 1k |      1000 |    mooncake |             typed |   true |               5440.9 |                 4.1 |
|       Multivariate 1k |      1000 |    mooncake |             typed |   true |               1011.2 |                 8.8 |
|   Loop univariate 10k |     10000 |    mooncake |             typed |   true |              61060.9 |                 3.7 |
|      Multivariate 10k |     10000 |    mooncake |             typed |   true |               8631.0 |                10.0 |
|               Dynamic |        10 |    mooncake |             typed |   true |                129.1 |                12.3 |
|              Submodel |         1 |    mooncake |             typed |   true |                 14.0 |                 6.3 |
|                   LDA |        12 | reversediff |             typed |   true |                444.4 |                 5.6 |

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.91%. Comparing base (0b6e364) to head (73ed741).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/test_utils/ad.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #935   +/-   ##
=======================================
  Coverage   82.91%   82.91%           
=======================================
  Files          36       36           
  Lines        3962     3962           
=======================================
  Hits         3285     3285           
  Misses        677      677           

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[coveralls]

Pull Request Test Coverage Report for Build 15210817349

Details

• 0 of 2 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 83.08%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/test_utils/ad.jl	0	2	0.0%

Totals
Change from base Build 15185827322:	0.0%
Covered Lines:	3285
Relevant Lines:	3954

---

💛 - Coveralls

[github-actions]

DynamicPPL.jl documentation for PR #935 is available at:
https://TuringLang.github.io/DynamicPPL.jl/previews/PR935/