@SuppressWarnings("unused")
        public AssertionsBuilder<I, O> withSingleArgTestFunction(final Function<I, O> testFunction) {
            Objects.requireNonNull(testFunction);
            return new AssertionsBuilder<>(testCase ->
                    testFunction.apply(testCase.getInput()));
        }
Define the action for the dynamic test lambda, where the test input
uses {@link TestCase#getInput()} to produce some output.
Test assertions are added later with {@link AssertionsBuilder#withAssertions(Consumer)}.
stroom-test-common/src/main/java/stroom/test/common/DynamicTestBuilder.java