@Test
  public void multple_parameters_and_block_body() throws Exception {
    ArrowFunctionTree tree = parse("(p1, p2) => p;", Kind.ARROW_FUNCTION);

    assertThat(tree.is(Kind.ARROW_FUNCTION)).isTrue();
    assertThat(tree.parameters().is(Kind.FORMAL_PARAMETER_LIST)).isTrue();
    assertThat(tree.doubleArrow().text()).isEqualTo(JavaScriptPunctuator.DOUBLEARROW.getValue());
    assertThat(expressionToString(tree.conciseBody())).isEqualTo("p");
  }
  @Test
  public void single_no_parenthesis_parameter_and_block_body() throws Exception {
    ArrowFunctionTree tree = parse("p => {};", Kind.ARROW_FUNCTION);

    assertThat(tree.is(Kind.ARROW_FUNCTION)).isTrue();
    assertThat(tree.parameters() instanceof IdentifierTree).isTrue();
    assertThat(((IdentifierTree) tree.parameters()).name()).isEqualTo("p");
    assertThat(tree.doubleArrow().text()).isEqualTo(JavaScriptPunctuator.DOUBLEARROW.getValue());
    assertThat(tree.conciseBody().is(Kind.BLOCK)).isTrue();
  }
  @Test
  public void single_no_parenthesis_parameter_and_expression_body() throws Exception {
    ArrowFunctionTree tree = parse("p => p;", Kind.ARROW_FUNCTION);

    assertThat(tree.is(Kind.ARROW_FUNCTION)).isTrue();
    assertThat(tree.parameters() instanceof IdentifierTree).isTrue();
    assertThat(((IdentifierTree) tree.parameters()).name()).isEqualTo("p");
    assertThat(tree.doubleArrow().text()).isEqualTo("=>");
    assertThat(expressionToString(tree.conciseBody())).isEqualTo("p");
  }