test: Add comprehensive test suite for video-audio-recording module

Added 83 test cases across 9 test files with 100% pass rate, covering
device detection, parsing, grouping, and complete workflow integration.

## What Was Done

### Refactoring for Testability
- Extracted `cj/recording--parse-pactl-output` from `cj/recording-parse-sources`
- Separated parsing logic from shell command execution
- Enables testing with fixture data instead of live system calls

### Test Fixtures Created
- `pactl-output-normal.txt` - All device types (built-in, USB, Bluetooth)
- `pactl-output-empty.txt` - Empty output
- `pactl-output-single.txt` - Single device
- `pactl-output-monitors-only.txt` - Only monitor devices
- `pactl-output-inputs-only.txt` - Only input devices
- `pactl-output-malformed.txt` - Invalid/malformed output

### Unit Tests (8 files, 78 test cases)
1. **test-video-audio-recording-friendly-state.el** (10 tests)
   - State name conversion: SUSPENDED→Ready, RUNNING→Active

2. **test-video-audio-recording-parse-pactl-output.el** (14 tests)
   - Parse raw pactl output into structured data
   - Handle empty, malformed, and mixed valid/invalid input

3. **test-video-audio-recording-parse-sources.el** (6 tests)
   - Shell command wrapper testing with mocked output

4. **test-video-audio-recording-detect-mic-device.el** (13 tests)
   - Documents bugs: Returns ID numbers instead of device names
   - Doesn't filter monitors (legacy function, not actively used)

5. **test-video-audio-recording-detect-system-device.el** (13 tests)
   - Works correctly: Returns full device names
   - Tests monitor detection with various device types

6. **test-video-audio-recording-group-devices-by-hardware.el** (12 tests)
   - CRITICAL: Bluetooth MAC address normalization (colons vs underscores)
   - Device pairing logic (mic + monitor from same hardware)
   - Friendly name assignment
   - Filters incomplete devices

7. **test-video-audio-recording-check-ffmpeg.el** (3 tests)
   - ffmpeg availability detection

8. **test-video-audio-recording-get-devices.el** (7 tests)
   - Auto-detection fallback logic
   - Error handling for incomplete detection

### Integration Tests (1 file, 5 test cases)
9. **test-integration-recording-device-workflow.el** (5 tests)
   - Complete workflow: parse → group → friendly names
   - Bluetooth MAC normalization end-to-end
   - Incomplete device filtering across components
   - Malformed data graceful handling

## Key Testing Insights

### Bugs Documented
- `cj/recording-detect-mic-device` has bugs (returns IDs, doesn't filter monitors)
- These functions appear to be legacy code not used by main workflow
- Tests document current behavior to catch regressions if fixed

### Critical Features Validated
- **Bluetooth MAC normalization**: Input uses colons (00:1B:66:C0:91:6D),
  output uses underscores (00_1B_66_C0_91_6D), grouping normalizes correctly
- **Device pairing**: Only devices with BOTH mic and monitor are included
- **Friendly names**: USB/PCI/Bluetooth patterns correctly identified

### Test Coverage
- Normal cases: Valid inputs, typical workflows
- Boundary cases: Empty, single device, incomplete pairs
- Error cases: Malformed input, missing devices, partial detection

## Test Execution
All tests pass: 9/9 files, 83/83 test cases (100% pass rate)

```bash
make test-file FILE=test-video-audio-recording-*.el
# All pass individually

# Integration test also passes
make test-file FILE=test-integration-recording-device-workflow.el
```

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

1 files changed, 151 insertions, 0 deletions

diff --git a/tests/test-video-audio-recording-detect-system-device.el b/tests/test-video-audio-recording-detect-system-device.el
new file mode 100644
index 00000000..bea20e8a
--- /dev/null
+++ b/tests/test-video-audio-recording-detect-system-device.el
@@ -0,0 +1,151 @@
+;;; test-video-audio-recording-detect-system-device.el --- Tests for cj/recording-detect-system-device -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Unit tests for cj/recording-detect-system-device function.
+;; Tests auto-detection of system audio monitor device from pactl output.
+;; Mocks shell-command-to-string to test regex matching logic.
+;;
+;; NOTE: This function works correctly - returns the full device name ending in .monitor.
+;; The regex \\([^\t\n]+\\.monitor\\) matches any non-tab/newline chars ending with .monitor,
+;; which correctly captures the device name field from pactl output.
+;;
+;; This function may not be actively used (parse-sources is preferred).
+;; Tests document current behavior to catch regressions.
+
+;;; Code:
+
+(require 'ert)
+
+;; Stub dependencies before loading the module
+(defvar cj/custom-keymap (make-sparse-keymap)
+  "Stub keymap for testing.")
+
+;; Now load the actual production module
+(require 'video-audio-recording)
+
+;;; Normal Cases
+
+(ert-deftest test-video-audio-recording-detect-system-device-normal-built-in-monitor-found ()
+  "Test detection of built-in system audio monitor.
+Returns full device name."
+  (let ((output "49\talsa_output.pci-0000_00_1f.3.analog-stereo.monitor\tPipeWire\ts32le 2ch 48000Hz\tSUSPENDED\n50\talsa_input.pci-0000_00_1f.3.analog-stereo\tPipeWire\ts32le 2ch 48000Hz\tSUSPENDED\n"))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        (should (stringp result))
+        (should (equal "alsa_output.pci-0000_00_1f.3.analog-stereo.monitor" result))))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-normal-usb-monitor-found ()
+  "Test detection of USB system audio monitor."
+  (let ((output "99\talsa_output.usb-0b0e_Jabra_SPEAK_510_USB_1C48F9C067D5020A00-00.analog-stereo.monitor\tPipeWire\ts16le 2ch 48000Hz\tSUSPENDED\n"))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        (should (stringp result))
+        (should (equal "alsa_output.usb-0b0e_Jabra_SPEAK_510_USB_1C48F9C067D5020A00-00.analog-stereo.monitor" result))))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-normal-bluetooth-monitor-found ()
+  "Test detection of Bluetooth monitor device."
+  (let ((output "81\tbluez_output.00_1B_66_C0_91_6D.1.monitor\tPipeWire\ts24le 2ch 48000Hz\tRUNNING\n"))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        (should (stringp result))
+        (should (equal "bluez_output.00_1B_66_C0_91_6D.1.monitor" result))))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-normal-first-match-returned ()
+  "Test that first matching monitor is returned when multiple exist."
+  (let ((output (concat "49\talsa_output.pci-0000_00_1f.3.analog-stereo.monitor\tPipeWire\ts32le 2ch 48000Hz\tSUSPENDED\n"
+                        "81\tbluez_output.00_1B_66_C0_91_6D.1.monitor\tPipeWire\ts24le 2ch 48000Hz\tRUNNING\n"
+                        "99\talsa_output.usb-device.monitor\tPipeWire\ts16le 2ch 48000Hz\tSUSPENDED\n")))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        ;; Returns first monitor device name
+        (should (equal "alsa_output.pci-0000_00_1f.3.analog-stereo.monitor" result))))))
+
+;;; Boundary Cases
+
+(ert-deftest test-video-audio-recording-detect-system-device-boundary-empty-output-returns-nil ()
+  "Test that empty output returns nil."
+  (cl-letf (((symbol-function 'shell-command-to-string)
+             (lambda (_cmd) "")))
+    (let ((result (cj/recording-detect-system-device)))
+      (should (null result)))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-boundary-only-inputs-returns-nil ()
+  "Test that output with only input devices (no monitors) returns nil."
+  (let ((output (concat "50\talsa_input.pci-0000_00_1f.3.analog-stereo\tPipeWire\ts32le 2ch 48000Hz\tSUSPENDED\n"
+                        "79\tbluez_input.00:1B:66:C0:91:6D\tPipeWire\tfloat32le 1ch 48000Hz\tSUSPENDED\n")))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        (should (null result))))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-boundary-whitespace-only-returns-nil ()
+  "Test that whitespace-only output returns nil."
+  (cl-letf (((symbol-function 'shell-command-to-string)
+             (lambda (_cmd) "  \n\t\n  ")))
+    (let ((result (cj/recording-detect-system-device)))
+      (should (null result)))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-boundary-monitor-different-states ()
+  "Test that monitors in different states are all matched."
+  (let ((output "81\tbluez_output.00_1B_66_C0_91_6D.1.monitor\tPipeWire\ts24le 2ch 48000Hz\tRUNNING\n"))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        ;; Should match regardless of state (RUNNING, SUSPENDED, IDLE)
+        (should (equal "bluez_output.00_1B_66_C0_91_6D.1.monitor" result))))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-boundary-case-insensitive-monitor ()
+  "Test that regex is case-insensitive for '.monitor' suffix.
+Documents that .MONITOR (uppercase) also matches."
+  (let ((output "49\talsa_output.pci-0000_00_1f.3.analog-stereo.MONITOR\tPipeWire\ts32le 2ch 48000Hz\tSUSPENDED\n"))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        ;; Case-insensitive: .MONITOR matches
+        (should (equal "alsa_output.pci-0000_00_1f.3.analog-stereo.MONITOR" result))))))
+
+;;; Error Cases
+
+(ert-deftest test-video-audio-recording-detect-system-device-error-malformed-output-returns-nil ()
+  "Test that malformed output returns nil."
+  (let ((output "This is not valid pactl output\nRandom text here\n"))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        (should (null result))))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-error-partial-monitor-matches ()
+  "Test that device with .monitor in middle partially matches (documents quirk).
+The regex matches up to first .monitor occurrence, even if not at end of device name."
+  (let ((output "50\talsa_input.monitor-device.analog-stereo\tPipeWire\ts32le 2ch 48000Hz\tSUSPENDED\n"))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        ;; QUIRK: Matches partial string "alsa_input.monitor"
+        (should (equal "alsa_input.monitor" result))))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-error-incomplete-line ()
+  "Test that incomplete lines with .monitor are still matched."
+  (let ((output "49\tincomplete-line.monitor\n"))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        ;; Should match device name ending in .monitor
+        (should (equal "incomplete-line.monitor" result))))))
+
+(ert-deftest test-video-audio-recording-detect-system-device-error-mixed-valid-invalid ()
+  "Test that mix of valid and invalid lines returns first valid monitor."
+  (let ((output (concat "invalid line without tabs\n"
+                        "49\talsa_output.pci-0000_00_1f.3.analog-stereo.monitor\tPipeWire\ts32le 2ch 48000Hz\tSUSPENDED\n"
+                        "another invalid line\n")))
+    (cl-letf (((symbol-function 'shell-command-to-string)
+               (lambda (_cmd) output)))
+      (let ((result (cj/recording-detect-system-device)))
+        (should (equal "alsa_output.pci-0000_00_1f.3.analog-stereo.monitor" result))))))
+
+(provide 'test-video-audio-recording-detect-system-device)
+;;; test-video-audio-recording-detect-system-device.el ends here