Add Groovy syntax test.

tests/syntax-tests/source/Groovy/test.groovy

@@ -0,0 +1,77 @@
+interface Display {
+    String asText()
+}
+
+trait Entity {
+    Integer id
+}
+
+class Product implements Entity, Display {
+    public String name
+    public Boolean available
+    public Float price
+
+    private String key
+    protected String data
+
+    /**
+     * Creates a new product instance.
+     * @param id Product ID.
+     * @param name Product name.
+     * @param available Product availability.
+     * @param price Product price.
+     * @param key Product key.
+     * @param data Product internal data.
+     */
+    Product(id, name, available, price, key = "key", data = "internal") {
+        this.id = id
+        this.name = name
+        this.available = available
+        this.price = price
+        this.key = key
+        this.data = data
+    }
+
+    /**@
+     * Returns product data as text.
+     * @return Data string.
+     */
+    String asText() {
+        return """ID [${id}] Name [${name}] Available [${available}] Price [${price}]"""
+    }
+}
+
+/* Creates a new product instance */
+def product = new Product(1, "T-Shirt", true, 15.00)
+
+println(product.asText())
+
+product.available = false
+product.price = 0.0
+
+// Check values
+assert product.asText() == "ID [1] Name [T-Shirt] Available [false] Price [0.0]"
+
+def factorial(Integer value) {
+    if (value <= 1) {
+        return 1
+    } else {
+        return value * factorial(value - 1)
+    }
+}
+
+assert factorial(5) == 120
+
+static String join(List<String> list, String separator) {
+    String data = ""
+
+    list.each { item ->
+        data += item + separator
+    }
+
+    data = data.substring(0, data.length() - 1)
+
+    return data
+}
+
+assert join(["g", "r", "o", "o", "v", "y"], " ") == "g r o o v y"