test(e2e): add discover and show-defaults command tests (#315)

Adds comprehensive E2E test coverage for two CLI commands that were previously untested:
- `discover` - Modbus device discovery with parameter scanning
- `show-defaults` - Display driver DEFAULT_CONFIG and SUPPORTED_CONFIG

Both commands are fully implemented and functional but lacked integration testing.

## Test Coverage

### show-defaults Command (7 tests)
- Help text display
- Default configuration display
- Supported configuration display  
- JSON format output with structure validation
- Support for both multi-device and single-device drivers
- Error handling for missing --driver option
- Error handling for non-existent drivers

### discover Command (7 tests)
- Help text display
- Quick strategy discovery with single device
- Multi-device discovery test
- JSON format output with structure validation
- Verbose mode showing progress messages
- Silent mode suppressing non-JSON output
- Error handling for missing --port option

## Implementation Notes

### Performance Optimization
All discover tests use restrictive parameters to minimize test execution time:
- `--max-devices 1` - Stop after finding first device (single-device tests)
- `--max-devices 2` - Find both devices (multi-device test)
- `--driver` flag - Use driver SUPPORTED_CONFIG to narrow parameter space
- `--strategy quick` - Test only common parameters

### Test Structure
Tests follow existing patterns from PR #285:
- Use emulator fixtures (port1-single-device, port2-multi-device)
- Validate both table and JSON output formats
- Include error handling and edge cases

## Verification

All 55 E2E tests pass:
```bash
cd tests/e2e
./run-tests.sh
# 55 tests, 0 failures
```

Closes #289

Author: groupsky

tests/e2e/fixtures/emulators/port2-multi-device.json

@@ -1,5 +1,5 @@
 {
-  "description": "XYMD1 temperature controller on port 2 (OR-WE-516 removed due to parity incompatibility)",
+  "description": "Two devices on port 2: XYMD1 and EX9EM (both use even parity)",
   "transport": {
     "type": "rtu",
     "port": "/tmp/ttyV2",
@@ -24,6 +24,33 @@
         "processingDelay": [1, 3],
         "perRegisterDelay": 0.1
       }
+    },
+    {
+      "slaveId": 2,
+      "deviceType": "EX9EM",
+      "registers": {
+        "holding": {
+          "0": 2200,
+          "1": 480,
+          "2": 500,
+          "3": 1050,
+          "4": 95,
+          "5": 1150,
+          "6": 950,
+          "7": 1111,
+          "8": 2222,
+          "9": 3333,
+          "10": 4444,
+          "42": 4,
+          "43": 2
+        }
+      },
+      "timing": {
+        "pollingInterval": 10,
+        "commandDetectionDelay": [2, 5],
+        "processingDelay": [1, 3],
+        "perRegisterDelay": 0.1
+      }
     }
   ]
 }

tests/e2e/tests/04-cli.bats

@@ -238,3 +238,176 @@ teardown() {
   assert_output_contains '"baudRate"'
   assert_output_contains '"parity"'
 }
+
+@test "show-defaults command shows help text" {
+  run node "$CLI_BIN" show-defaults --help
+  assert_success
+  assert_output_contains "show-defaults"
+  assert_output_contains "--driver"
+  assert_output_contains "--format"
+}
+
+@test "show-defaults displays driver configuration" {
+  run node "$CLI_BIN" show-defaults \
+    --driver @ya-modbus/driver-ex9em
+
+  assert_success
+  assert_output_contains "DEFAULT_CONFIG"
+  assert_output_contains "baudRate"
+  assert_output_contains "9600"
+  assert_output_contains "parity"
+  assert_output_contains "even"
+}
+
+@test "show-defaults displays supported configuration" {
+  run node "$CLI_BIN" show-defaults \
+    --driver @ya-modbus/driver-ex9em
+
+  assert_success
+  assert_output_contains "SUPPORTED_CONFIG"
+  assert_output_contains "validBaudRates"
+  assert_output_contains "validParity"
+}
+
+@test "show-defaults outputs JSON format" {
+  run node "$CLI_BIN" show-defaults \
+    --driver @ya-modbus/driver-ex9em \
+    --format json
+
+  assert_success
+
+  # Validate JSON structure
+  echo "$output" | jq -e 'has("defaultConfig")'
+  echo "$output" | jq -e 'has("supportedConfig")'
+  echo "$output" | jq -e '.defaultConfig.baudRate == 9600'
+  echo "$output" | jq -e '.defaultConfig.parity == "even"'
+}
+
+@test "show-defaults works with single-device driver" {
+  run node "$CLI_BIN" show-defaults \
+    --driver @ya-modbus/driver-or-we-516
+
+  assert_success
+  assert_output_contains "DEFAULT_CONFIG"
+  assert_output_contains "baudRate"
+  assert_output_contains "9600"
+  assert_output_contains "parity"
+  assert_output_contains "odd"
+}
+
+@test "show-defaults fails without --driver" {
+  run node "$CLI_BIN" show-defaults
+
+  assert_failure
+  assert_output_contains "driver"
+}
+
+@test "show-defaults fails with non-existent driver" {
+  run node "$CLI_BIN" show-defaults \
+    --driver @ya-modbus/driver-nonexistent
+
+  assert_failure
+  assert_output_contains "Driver package not found"
+}
+
+@test "discover command shows help text" {
+  run node "$CLI_BIN" discover --help
+  assert_success
+  assert_output_contains "discover"
+  assert_output_contains "--port"
+  assert_output_contains "--strategy"
+  assert_output_contains "--driver"
+}
+
+@test "discover finds single device with quick strategy" {
+  run start_test_emulator "fixtures/emulators/port1-single-device.json"
+  assert_success
+  EMULATOR_PID="$output"
+
+  run node "$CLI_BIN" discover \
+    --port /tmp/ttyV1 \
+    --driver @ya-modbus/driver-ex9em \
+    --strategy quick \
+    --max-devices 1
+
+  assert_success
+  assert_output_contains "Found 1 device"
+  assert_output_contains "Slave ID 1"
+  assert_output_contains "9600"
+}
+
+@test "discover finds multiple devices" {
+  run start_test_emulator "fixtures/emulators/port2-multi-device.json"
+  assert_success
+  EMULATOR_PID="$output"
+
+  run node "$CLI_BIN" discover \
+    --port /tmp/ttyV3 \
+    --strategy quick \
+    --max-devices 2
+
+  assert_success
+  assert_output_contains "Found 2 device"
+  assert_output_contains "Slave ID 1"
+  assert_output_contains "Slave ID 2"
+}
+
+@test "discover outputs JSON format" {
+  run start_test_emulator "fixtures/emulators/port1-single-device.json"
+  assert_success
+  EMULATOR_PID="$output"
+
+  run node "$CLI_BIN" discover \
+    --port /tmp/ttyV1 \
+    --driver @ya-modbus/driver-ex9em \
+    --strategy quick \
+    --max-devices 1 \
+    --silent \
+    --format json
+
+  assert_success
+  echo "$output" | jq -e '.[0].slaveId == 1'
+  echo "$output" | jq -e '.[0].baudRate == 9600'
+}
+
+@test "discover with verbose shows progress" {
+  run start_test_emulator "fixtures/emulators/port1-single-device.json"
+  assert_success
+  EMULATOR_PID="$output"
+
+  run node "$CLI_BIN" discover \
+    --port /tmp/ttyV1 \
+    --driver @ya-modbus/driver-ex9em \
+    --strategy quick \
+    --max-devices 1 \
+    --verbose
+
+  assert_success
+  assert_output_contains "Testing"
+}
+
+@test "discover with silent suppresses progress" {
+  run start_test_emulator "fixtures/emulators/port1-single-device.json"
+  assert_success
+  EMULATOR_PID="$output"
+
+  run node "$CLI_BIN" discover \
+    --port /tmp/ttyV1 \
+    --driver @ya-modbus/driver-ex9em \
+    --strategy quick \
+    --max-devices 1 \
+    --silent \
+    --format json
+
+  assert_success
+  # Output should only be JSON, no progress messages
+  echo "$output" | jq -e 'type == "array"'
+}
+
+@test "discover fails without --port" {
+  run node "$CLI_BIN" discover \
+    --driver @ya-modbus/driver-ex9em
+
+  assert_failure
+  assert_output_contains "port"
+}