Add unit tests for deploy.ts and compiler utilities with Vitest #79

Summary

The test suite currently has no coverage of the critical paths that matter most: the multi-step deployContract() pipeline, the Soroban simulation flow, the full compile-to-WASM codegen pipeline, and the graph persistence/import/export layer. This issue defines and implements a comprehensive test coverage plan across all four layers with mock strategies, edge case coverage, and a coverage gate enforced in CI.

Why This Is Hard

• Mocking the Stellar SDK: deployContract() calls SorobanRpc.Server, Horizon.Server, TransactionBuilder, and the Freighter API across three async stages. Setting up correct mocks that simulate both the happy path and the five failure modes (wallet rejection, simulation error, upload collision, tx poll timeout, chain failure) requires careful dependency injection design.
• Codegen correctness is combinatorial: generateContractSource has 6 block types × 3 param combinations × 2 execution order variants. Testing all meaningful combinations without writing 50 copy-paste test cases requires parameterised test factories.
• The compile/validate pipeline has subtle invariants: validateContractGraph has 5 validation passes. Each pass can fail independently or in combination. Tests must cover single-pass failures, multi-pass failures, and valid graphs that must not regress.
• Coverage gate: the CI pipeline must fail if coverage drops below 80% on the src/lib/compile/ and src/lib/stellar/ directories. Setting this up correctly in Vitest requires per-directory thresholds in vitest.config.ts, which is non-trivial configuration.
• Test isolation: localStorage is shared across tests. Graph persistence tests must reset state in beforeEach to avoid flaky cross-test contamination.

Test Plan by Module

src/lib/stellar/deploy.ts

src/lib/stellar/simulate.ts

src/lib/compile/codegen.ts

src/lib/compile/validate.ts

src/lib/editor/graphPersistence.ts

Coverage Gate

vitest.config.ts must set:

coverage: {
  thresholds: {
    "src/lib/compile/": { lines: 80, functions: 80 },
    "src/lib/stellar/": { lines: 80, functions: 80 },
    "src/lib/editor/": { lines: 75, functions: 75 },
  }
}

CI fails if any threshold is not met.

Acceptance Criteria

• All test cases in the table above are implemented and passing.
• vi.mock("@stellar/freighter-api", ...) is used for all wallet-dependent tests — no real extension calls.
• SorobanRpc.Server and Horizon.Server are mocked via vi.mock("@stellar/stellar-sdk", ...).
• localStorage is cleared in beforeEach for all graph persistence tests.
• Coverage thresholds are configured in vitest.config.ts and enforced in CI.
• npm run test:coverage runs and produces a coverage report.
• No test uses setTimeout with real delays — async resolution is mocked.
• All 30+ test cases are parameterised where possible (no copy-paste test bodies).
• All existing tests continue to pass and the CI pipeline remains green.