test: add alert module tests for different welcome_message configurations (#3867)

In this way, all options for `welcome_message` are tested.

tests/configs/modules/alert/welcome_false.js

@@ -0,0 +1,18 @@
+let config = {
+	address: "0.0.0.0",
+	ipWhitelist: [],
+	modules: [
+		{
+			module: "alert",
+			config: {
+				display_time: 1000000,
+				welcome_message: false
+			}
+		}
+	]
+};
+
+/*************** DO NOT EDIT THE LINE BELOW ***************/
+if (typeof module !== "undefined") {
+	module.exports = config;
+}

tests/configs/modules/alert/welcome_string.js

@@ -0,0 +1,18 @@
+let config = {
+	address: "0.0.0.0",
+	ipWhitelist: [],
+	modules: [
+		{
+			module: "alert",
+			config: {
+				display_time: 1000000,
+				welcome_message: "Custom welcome message!"
+			}
+		}
+	]
+};
+
+/*************** DO NOT EDIT THE LINE BELOW ***************/
+if (typeof module !== "undefined") {
+	module.exports = config;
+}