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Room, HTTP, WorkManager, and migration tests

Fakes test policy quickly. Real adapters test the contracts fakes cannot reproduce: SQL, serialization, HTTP details, scheduler mapping, and schema evolution.

Room DAO behavior​

Use an isolated test database and verify actual query semantics:

@Test
fun latestOrders_areTenantScopedAndDeterministic() = runTest {
    dao.insertAll(order("B", tenant="T1", at=instant),
                  order("A", tenant="T1", at=instant),
                  order("X", tenant="T2", at=instant))

    assertEquals(listOf("A", "B"), dao.latest("T1").map { it.id })
}

Test empty/null, conflicts, transactions/rollback, foreign keys/cascade, ordering ties, pagination, Flow invalidation, concurrent operations, and account isolation. Android/device SQLite tests provide higher fidelity than mocking DAO.

Migration tests​

Export schemas in version control. Build each supported old schema/database fixture, insert representative and boundary data, run migration to current, validate schema, and assert data/invariants/indexes/defaults.

v3 -> current
v4 -> current
v5 -> current

Testing only v5→v6 misses users upgrading from older installed versions. Include destructive migration only when data loss is an explicit acceptable product decision.

MockWebServer​

server.enqueue(
    MockResponse()
        .setResponseCode(200)
        .setHeader("Content-Type", "application/json")
        .setBody(orderJson)
)

val result = api.order("O-1")
val request = server.takeRequest()
assertEquals("/orders/O-1", request.path)
assertEquals("Bearer test-access", request.getHeader("Authorization"))

Test headers/path/query/body/encoding, unknown/missing/null fields, non-2xx error body, empty body, timeout/disconnect, large/streamed response, redirects, retry/idempotency, cancellation, and sensitive-header logging. TLS/config integration may need an additional higher-fidelity test.

WorkManager​

Separate:

  • use-case unit test (business result);
  • Worker adapter test (input → use case → Result mapping/progress/cancellation);
  • scheduling test (unique name/policy, constraints, tags, backoff, chain);
  • integration/device test (constraints/lifecycle if risk warrants).

Use WorkManager testing helpers to initialize test driver/executor and mark constraints/delay as met. Verify retryable versus permanent failures and idempotency across repeated execution.

Integration fixture hygiene​

Each test owns server/database/files/account/time. Close database/server/dispatchers; delete temporary data; never share sequence-dependent fixtures. Emit useful artifacts on failure (requests/schema/state) without secrets.

Migration tests protect user data

A migration that “builds successfully” can still drop rows, change null/default semantics, remove indexes, or violate tenant boundaries. Test data meaning, not only schema validation.

Sources​

Exercise​

Test offline order sync where server accepts a mutation then disconnects: worker retries, idempotency prevents duplicate, Room moves outbox to confirmed, and migration preserves pending rows.