# `DoubleDown.DynamicFacade.Cover`
[🔗](https://github.com/mccraigmccraig/double_down/blob/main/lib/double_down/dynamic_facade/cover.ex#L1)

Ensures DynamicFacade-shimmed modules retain `:cover` instrumentation.

When ExCoverall or `:cover` compiles a module with coverage instrumentation,
`DynamicFacade.setup/1` renames the on-disk (non-instrumented) bytecode to
`Module.__dd_original__`, stripping coverage from the backup. This module
preserves coverage by:

  1. Exporting pre-shim coverdata
  2. Re-instrumenting the backup via `:cover.compile_beams/1`
  3. Providing `merge/1` to rewrite backup coverdata back to the original name

# `merge`

Merge coverdata from the `__dd_original__` backup into the original module name.

Exports coverdata for `Module.__dd_original__`, rewrites all module-name
references back to `Module`, imports the result, and cleans up the temp file.

Call this after all tests have completed to ensure ExCoverall sees coverage
for DynamicFacade-shimmed modules under their original names.

# `merge_all`

Merge coverdata for all registered DynamicFacade modules.

Iterates all modules set up via `DynamicFacade.setup/1` and calls
`merge/1` for each. No-op if `:cover` is not available or has no
instrumented modules.

Call this from `test/test_helper.exs` after all tests complete:

    ExUnit.after_suite(fn _ -> DoubleDown.DynamicFacade.Cover.merge_all() end)

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*Consult [api-reference.md](api-reference.md) for complete listing*