Assertion density is reasonable per test

When the average assertion-to-test-block ratio falls below 1.0, the majority of test blocks have no assertions at all. This isn't a style issue — it means most of your test suite is exercising code paths without checking outcomes. Coverage tools will report lines as "covered" while the behavior of those lines remains completely unverified. ISO-25010:2011 testability requires that tests can detect deviations from specified behavior; a test block with no assertion can never detect anything.

Audit each it/test block and add at least one expect call that checks the actual output or state change produced by the code under test. Aim for a ratio above 1.0 project-wide:

// Before: exercises code, verifies nothing
it('finds user by id', async () => {
  await service.find('user-1')
})

// After: asserts identity and shape
it('finds user by id', async () => {
  const found = await service.find('user-1')
  expect(found?.id).toBe('user-1')
  expect(found?.email).toBeDefined()
})

• ID: assertion-density-reasonable

• Severity: medium

• What to look for: Walk all test files. For each test file, count all it(/test(/Deno.test( blocks AND count all assertion calls (any pattern from check 1). Compute the ratio: assertion_calls / test_blocks. A ratio of less than 1.0 means many test blocks have zero assertions on average. Report files where the ratio is below 1.0.

• Pass criteria: Average assertion-per-test ratio across the project is at least 1.0. Report: "X test blocks across Y test files, Z total assertions, ratio: A.A per test."

• Fail criteria: Average assertion ratio is below 1.0 — most tests have no assertions.

• Skip (N/A) when: Project has 0 test files.

• Detail on fail: "Average assertion ratio is 0.4 — 50 test blocks across 10 files have only 20 total assertions. Most tests have no assertion."

• Remediation: A test without an assertion is just a code-coverage line counter — it exercises the function but doesn't verify anything. Add at least 1 assertion per test:

  describe('UserService', () => {
    it('creates a user', async () => {
      const user = await service.create({ email: 'a@b.com' })
      expect(user.id).toBeDefined()
    })
  
    it('finds a user by id', async () => {
      const found = await service.find('user-1')
      expect(found?.id).toBe('user-1')
    })
  })