feat: Add support for step argument (#149)

features/argument.feature

@@ -0,0 +1,21 @@
+Feature: Argument feature
+  Scenario: compare text with argument
+    When I concat text "Hello " and argument:
+      """
+      World!
+      """
+    Then the result should equal argument:
+      """
+      Hello World!
+      """
+  Scenario: compare text with multiline argument
+    When I concat text "Hello " and argument:
+      """
+      New
+      World!
+      """
+    Then the result should equal argument:
+      """
+      Hello New
+      World!
+      """

gobdd.go

@@ -541,6 +541,9 @@ func (s *Suite) runStep(ctx Context, t *testing.T, step *msgs.GherkinDocument_Fe
 	}
 
 	params := def.expr.FindSubmatch([]byte(step.Text))[1:]
+	if argument, ok := step.Argument.(*msgs.GherkinDocument_Feature_Step_DocString_); ok {
+		params = append(params, []byte(argument.DocString.Content))
+	}
 	t.Run(fmt.Sprintf("%s %s", strings.TrimSpace(step.Keyword), step.Text), func(t *testing.T) {
 		// NOTE consider passing t as argument to step hooks
 		ctx.Set(TestingTKey{}, t)

gobdd_test.go

@@ -68,6 +68,14 @@ func TestParameterTypes(t *testing.T) {
 	suite.Run()
 }
 
+func TestArguments(t *testing.T) {
+	suite := NewSuite(t, WithFeaturesPath("features/argument.feature"))
+	suite.AddStep(`the result should equal argument:`, checkt)
+	suite.AddStep(`I concat text {text} and argument:`, concat)
+
+	suite.Run()
+}
+
 func TestScenarioOutlineExecutesAllTests(t *testing.T) {
 	c := 0
 	suite := NewSuite(t, WithFeaturesPath("features/outline.feature"))