lsp: add 'Hexai: implement unit test' code action for Gov0.4.1

- Generate or append tests to _test.go
- Jump to generated test via showDocument (command + server-initiated)
- Document the feature in docs/go-unit-tests.md
- Prefix action titles with 'Hexai: '
- Bump version to 0.4.1

2 files changed, 28 insertions, 0 deletions

diff --git a/docs/go-unit-tests.md b/docs/go-unit-tests.md
new file mode 100644
index 0000000..1be9fd0
--- /dev/null
+++ b/docs/go-unit-tests.md
@@ -0,0 +1,27 @@
+# Go unit tests via code action
+
+Hexai can generate Go unit tests for the function at your cursor.
+
+- Scope: Available only for Go source files ending with `.go` (not `_test.go`).
+- Trigger: Use your editor's code actions on the current selection/position and pick "Implement unit test".
+
+What happens
+
+- Function detection: Hexai finds the nearest `func` definition above the cursor and captures the function body by balancing braces.
+- Test generation:
+  - If an LLM provider is configured, Hexai asks it to generate one or more `Test*` functions using the `testing` package. The provider must return only the test function code (no package/import lines).
+  - If no provider is configured or the request fails, Hexai inserts a small stub test `Test<Name>` with a TODO.
+- File handling and navigation:
+  - If `<file>_test.go` exists, the test function is appended to the end of that file.
+  - If it does not exist, Hexai creates it, writing `package <pkg>` (inferred from the source file) and `import "testing"`, followed by the generated test function(s).
+  - After applying the edit, Hexai asks the editor to focus the test file and place the cursor at the start of the newly added test function.
+
+Notes and limitations
+
+- Imports on append: when appending to an existing test file, Hexai assumes `testing` is available. If not, add `import "testing"` to the test file and re-run `go test`.
+- Method names: for methods with receivers, test names default to `TestMethod` (stub fallback). Future improvement may generate `TestType_Method` automatically.
+- Formatting: run `go fmt ./...` or your editor's formatter to normalize whitespace if needed.
+
+Examples
+
+In Helix, position the cursor inside a function and invoke code actions; choose "Implement unit test". Hexai will create or update `<file>_test.go` accordingly.
diff --git a/docs/usage-examples.md b/docs/usage-examples.md
index 5a80b18..3e96ade 100644
--- a/docs/usage-examples.md
+++ b/docs/usage-examples.md
@@ -65,6 +65,7 @@ Operate on the current selection in Helix:
 
 - Rewrite selection: finds the first instruction inside the selection and rewrites accordingly.
 - Resolve diagnostics: gathers only diagnostics overlapping the selection and fixes them by editing the selected code; diagnostics outside the selection are not changed.
+- Implement unit test (Go): when editing a `.go` file, adds a code action to generate a unit test for the function under the cursor. If `<file>_test.go` exists, appends a new `Test*`; otherwise creates the test file with `package` and `import "testing"`.
 
 Instruction sources (first match wins):