Abstract: A data processing system defines a unit test for a dataflow graph comprising a plurality of executable components. The system receives an indication of a portion of a dataflow graph for testing. The system receives a parameter set indicating expected output data to be generated by execution of a component of the graph. The system receives input data for the component. The input data are indicated by the parameter set and configured to test a functionality of the component. The system defines a unit test of the component based on the parameter set. The unit test provides the input data to inputs of the dataflow graph, causes processing of the input data by the component of the dataflow graph to generate output data, and generates results data indicating a correspondence between the output data and the expected output data indicated by the parameter.