VariableDeclaration variableA = functionMain.getChild(0);
assertEquals("a", variableA.getName());
VariableDeclaration variableB = functionMain.getChild(1);
assertEquals("b", variableB.getName());
ExpressionStatement statement = functionMain.getChild(2);
Expression expression = statement.getExpression(0);
assertTrue(expression instanceof AssignmentExpression);
AssignmentExpression assignment = (AssignmentExpression) expression;
Name leftSide = assignment.getExpression(0);
Name rightSide = assignment.getExpression(1);
assertEquals("a", leftSide.getIdentifier());