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testing: validate both JSON and HCL synth output in core unit tests, not just JSON snapshots #563
Description
Description
Most unit tests in packages/cdktn/test snapshot JSON synth output. Nothing checks that the output is valid Terraform, and the HCL path is rarely checked at all. Several recent bugs were visible in snapshots or only affected HCL, and none failed a test:
- VariableType.tuple() renders invalid HCL: tuple(a, b) instead of tuple([a, b]) #521:
tuple(a, b)was in thetuple typesnapshot for years. - fix(lib): HCL synth corrupts or drops core blocks (terraform{} extras, top-level overrides, lifecycle conditions) #313: three HCL-only defects. Its notes say "the current test suites mostly assert JSON synth".
- fix(lib): Handle null variable defaults #541:
default: nullis dropped in HCL but kept in JSON. - HCL synth doesn't escape backslashes in strings: the default local backend path on Windows produces invalid cdk.tf #562: backslashes aren't escaped in HCL strings, so the default local backend path is invalid on Windows.
Proposal
Add a shared helper that synthesizes a stack in both modes and runs toBeValidTerraform on each, then use it in the suites that cover core blocks (variables, outputs, locals, backends, lifecycle, moved/import/removed).
- A provider-free stack validates in about 0.5s with no network:
init -backend=falseplusvalidate. I tried this on a variable stack with Terraform 1.14.3 and OpenTofu 1.12.6. CI already runs the unit tests against Terraform 1.5.7, 1.16.1 and OpenTofu 1.12.6. - On a machine without the binary, the helper could fall back to snapshot-only, the same way other tests auto-skip.
- On Windows, HCL validation will fail on the backend block until HCL synth doesn't escape backslashes in strings: the default local backend path on Windows produces invalid cdk.tf #562 is fixed.
Testing.app({ hclOutput: true })doesn't produce HCL today (App({ hclOutput: true }) is ignored: the stack writes JSON into cdk.tf #561), so the helper would have to setSYNTH_HCL_OUTPUTaround stack construction until that's fixed.
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