[omermorad]

Sociable tests cannot currently construct real implementations behind string, symbol, or abstract-class dependency tokens. Add an explicit binding while retaining existing Unit v4 behavior:

const { unit, unitRef } = await TestBed.sociable(CheckoutService)
  .expose(PRICING, PricingService)
  .mock(ExchangeRates)
  .impl((stub) => ({ rate: stub().mockReturnValue(1.2) }))
  .compile();

Fixes #464. This is an additive Unit v4 feature.

Craig's original contribution

This continues @craig0990's proposal and implementation in #465. Commit 477ae5c4 ports his original 211ed87d181e4bba1ca00bd29371663648820c1f and preserves Craig Roberts's Git authorship and original author date, with the source commit recorded in the message. The author email uses Craig's public GitHub-linked identity, as verified on his earlier merged contribution #529, so GitHub attributes the commit to @craig0990. The port resolves conflicts against the current architecture and retains the existing array-based core contracts. Follow-up validation, abstract-token support, documentation, and packed-consumer coverage are separate commits.

Behavior

• .expose(Class) retains its existing behavior. .expose(token, Implementation) constructs the supplied implementation for a string, symbol, abstract-class, or concrete-class token.
• Class-token implementations are checked against the token's instance type. Plain strings and symbols do not independently encode an interface type.
• Repeated requests for the same token and metadata share an instance. Different tokens or metadata qualifiers remain independent, including when their implementation class is the same. A token binding does not implicitly expose or alias its implementation's class token.
• A binding applies across that token's metadata qualifiers. Qualified .mock(...).auto(), .impl(), and .final() declarations can replace individual occurrences and take precedence over exposure.
• Unexposed dependencies retain ordinary v4 automatic mocking. Exposed instances are accessed through the unit; unitRef.get() remains for mocks.
• Reject conflicting implementation declarations, report token constructor cycles, and warn about unreachable bindings.
• Keep token exposure in selective sociable mode. Combining it with .compose() remains unsupported. This PR does not add fail-fast behavior or change defaults.

The test supplies the binding explicitly. Suites does not inspect or verify the production container's registration, so tests must keep their chosen implementation aligned with production wiring when that is relevant.

Compatibility and release

Existing core array parameters, custom construction strategies, and DI/doubles adapter contracts are retained. Bindings use an optional resolver setting; new resolution results and constructor parameters are additive. No adapter package changes or manual version/changelog edits are included.

The repository's actual conventional-commit release preset recommends minor bumps for @suites/core.unit and @suites/unit from this PR, with no breaking-change notes. Preserve the authored conventional commits when merging.

Validation

• Frozen-lockfile install, full build, lint, and package tests passed locally on Node 26.13.0.
• Final core run: 105 tests passed, including the existing integration suites and new binding regressions.
• All ten packed consumers passed runtime suites and both normal/skipLibCheck typecheck variants across Jest/Vitest, NestJS/Inversify/InjectionJS, and supported CJS/ESM combinations.
• New consumer coverage verifies string/symbol/abstract bindings, nested construction, identity, qualified overrides, property injection where supported, normal automatic mocks, and negative type assertions for incompatible or abstract implementations and lost subject inference.
• Independent runtime and typing reviews completed. The typing review identified a compiler-floor regression, now corrected and covered by a TypeScript 5.2.2 fixture with skipLibCheck: false. The reviewer verified that the fixture fails against the previous declarations and passes with the correction.
• Hosted Node 22/24/26 validation for the updated head is pending. This PR is a draft for review; nothing has been merged or released.

[codecov]

Codecov Report

❌ Patch coverage is 97.87234% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 93.26%. Comparing base (074388f) to head (4b49d2a).

Files with missing lines	Patch %	Lines
...ore/src/services/builders/sociable-unit-builder.ts	94.44%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1121      +/-   ##
==========================================
+ Coverage   92.84%   93.26%   +0.41%     
==========================================
  Files          27       29       +2     
  Lines         615      668      +53     
  Branches      105      118      +13     
==========================================
+ Hits          571      623      +52     
  Misses         27       27              
- Partials       17       18       +1     

Flag	Coverage Δ
core.unit	96.85% <97.87%> (-0.02%)	⬇️
di.injectionjs	100.00% <ø> (?)
di.inversify	87.73% <ø> (ø)
di.nestjs	87.25% <ø> (ø)
doubles.jest	100.00% <ø> (ø)
doubles.vitest	97.05% <ø> (ø)
unit	84.00% <ø> (ø)

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