Add headless browser support to runs

src/org/moodle/ci/browsers/Browser.groovy

@@ -5,7 +5,12 @@ class Browser {
 
     protected String defaultTags
 
-    def getName() {
+    public boolean headless
+
+    String getName() {
+        if (headless) {
+            return "headless${name}"
+        }
         return name
     }
 

test/org/moodle/ci/browsers/Chrome.groovy

+package test.org.moodle.ci.browsers;
+
+import spock.lang.Specification
+
+class Chrome extends Specification {
+    def "Default tags are @javascript"() {
+        given:
+        def browser = new org.moodle.ci.browsers.Chrome();
+
+        when:
+        def output = browser.getDefaultTags()
+
+        then:
+        assert output == "@javascript"
+    }
+
+    def "Name is chrome"() {
+        given:
+        def browser = new org.moodle.ci.browsers.Chrome();
+
+        when:
+        def output = browser.name
+
+        then:
+        assert output == "chrome"
+    }
+
+    def "Name is chrome when not headless"() {
+        given:
+        def browser = new org.moodle.ci.browsers.Chrome();
+
+        when:
+        browser.headless = false
+        def output = browser.name
+
+        then:
+        assert output == "chrome"
+    }
+    def "Name is headlesschrome when headless"() {
+        given:
+        def browser = new org.moodle.ci.browsers.Chrome();
+
+        when:
+        browser.headless = true
+        def output = browser.name
+
+        then:
+        assert output == "headlesschrome"
+    }
+}