@Test
    public void testCatAndVariableExpression_simple() {
        var tester = new ScriptTester();
        var expression = tester.expressionFrom(
                "input myString | (get_var A | to_array) . (get_var B | to_array) | attribute myStringArray");

        SimpleTestAdapter adapter = new SimpleTestAdapter();
        adapter.createField(new Field("myString", DataType.STRING));
        adapter.createField(new Field("myStringArray", ArrayDataType.getArray(DataType.STRING)));

        var verificationContext = new TypeContext(adapter);
        verificationContext.setVariableType("A", DataType.STRING);
        verificationContext.setVariableType("B", DataType.STRING);
        expression.resolve(verificationContext);

        var context = new ExecutionContext(adapter);
        context.setVariable("A", new StringFieldValue("value 4"));
        context.setVariable("B", new StringFieldValue("value 5"));
        expression.execute(context);
        assertEquals("[value 4, value 5]", adapter.values.get("myStringArray").toString());
    }
@author Simon Thoresen Hult
@author bratseth
indexinglanguage/src/test/java/com/yahoo/vespa/indexinglanguage/ScriptTestCase.java