Unit test, and correct, stack

sql/parser.go

@@ -25,7 +25,7 @@ func (s *stack) pop() rune {
 		return rune(0)
 	}
 	c := s.c[len(s.c)-1]
-	s.c = s.c[:len(s.c)]
+	s.c = s.c[:len(s.c)-1]
 	return c
 }
 

sql/parser_test.go

@@ -10,3 +10,55 @@ func Test_ScannerNew(t *testing.T) {
 		t.Fatalf("failed to create basic Scanner")
 	}
 }
+
+func Test_stackEmpty(t *testing.T) {
+	s := newStack()
+	if !s.empty() {
+		t.Fatal("new stack is not empty")
+	}
+
+	if s.peek() != rune(0) {
+		t.Fatal("peek of empty stack does not return correct value")
+	}
+}
+
+func Test_stackSingle(t *testing.T) {
+	s := newStack()
+	s.push('x')
+	if s.empty() {
+		t.Fatal("non-empty stack marked as empty")
+	}
+
+	if s.peek() != 'x' {
+		t.Fatal("peek of single stack does not return correct value")
+	}
+
+	if s.pop() != 'x' {
+		t.Fatal("pop of single stack does not return correct value")
+	}
+
+	if !s.empty() {
+		t.Fatal("popped stack is not empty")
+	}
+}
+
+func Test_stackMulti(t *testing.T) {
+	s := newStack()
+	s.push('x')
+	s.push('y')
+	s.push('z')
+
+	if s.pop() != 'z' {
+		t.Fatal("pop of 1st multi stack does not return correct value")
+	}
+	if s.pop() != 'y' {
+		t.Fatal("pop of 2nd multi stack does not return correct value")
+	}
+	if s.pop() != 'x' {
+		t.Fatal("pop of 3rd multi stack does not return correct value")
+	}
+
+	if !s.empty() {
+		t.Fatal("popped multi stack is not empty")
+	}
+}