chore: Claude

Author: krlmlr

.Rbuildignore

@@ -35,3 +35,4 @@
 ^renovate\.json$
 ^tests/testthat/helper-sync\.R$
 ^index\.md$
+^CLAUDE\.md$

CLAUDE.md

@@ -0,0 +1,23 @@
+# Claude Development Notes for dm Package
+
+This file contains important notes and best practices for working with the dm package codebase.
+
+## Testing Guidelines
+
+### Use test_local() with filter argument for specific test files
+
+Always use the `filter` argument when running specific test files to avoid running all tests:
+
+```r
+# Run specific test files
+testthat::test_local(filter = "flatten")     # Runs test-flatten.R
+
+# Run all tests (only when necessary)
+testthat::test_local()
+```
+
+**Important**: The `filter` argument filters by test file names, not individual test names within files.
+
+---
+
+*This file should be updated as new patterns are discovered.*