chore: update karma config for hydration tests

Author: divmain

package.json

@@ -25,6 +25,7 @@
         "test:ci": "vitest run --workspace vitest.workspace.mjs --coverage",
         "test:karma": "nx test @lwc/integration-karma",
         "test:karma:start": "nx start @lwc/integration-karma",
+        "test:hydration": "nx hydration:test @lwc/integration-karma",
         "test:hydration:start": "nx hydration:start @lwc/integration-karma",
         "test:integration": "nx sauce @lwc/integration-tests",
         "test:performance": "nx test @lwc/perf-benchmarks",

packages/@lwc/integration-karma/package.json

@@ -10,7 +10,7 @@
         "hydration:sauce:engine-server": "ENGINE_SERVER=true karma start ./scripts/karma-configs/hydration/sauce.js --single-run",
         "hydration:sauce:ci:engine-server": "ENGINE_SERVER=true ../../../scripts/ci/retry.sh karma start ./scripts/karma-configs/hydration/sauce.js --single-run",
         "hydration:start": "KARMA_MODE=watch karma start ./scripts/karma-configs/hydration/local.js",
-        "hydration:test": "karma start ./scripts/karma-configs/hydration/local.js --single-run --browsers ChromeHeadless",
+        "hydration:test": "karma start ./scripts/karma-configs/hydration/local.js --single-run",
         "hydration:sauce": "karma start ./scripts/karma-configs/hydration/sauce.js --single-run",
         "hydration:sauce:ci": "../../../scripts/ci/retry.sh karma start ./scripts/karma-configs/hydration/sauce.js --single-run",
         "sauce": "karma start ./scripts/karma-configs/test/sauce.js --single-run",

packages/@lwc/integration-karma/scripts/karma-configs/hydration/local.js

@@ -14,8 +14,8 @@ module.exports = (config) => {
     config.set({
         reporters: [...config.reporters, 'progress'],
 
-        browsers: ['Chrome'],
+        browsers: ['ChromeHeadless', 'FirefoxHeadless'],
 
-        plugins: [...config.plugins, 'karma-chrome-launcher'],
+        plugins: [...config.plugins, 'karma-chrome-launcher', 'karma-firefox-launcher'],
     });
 };