In order to test digital modules with functional elements, these are divided into test units (3) which respectively have inputs and outputs. Alternating test patterns are applied to the inputs of the test unit (3), and the test responses resulting from this are evaluated at the outputs of the test unit (3). The effect is then encountered that changes at each of the inputs of a test unit (3) do not all affect a particular output of this test unit (3). For every output of the test unit (3), it is possible to define a cone (5) whose apex is formed by the particular output of the test unit (3) and whose base comprises the inputs of the test unit (3) where, and only where, changes affect the particular output. According to the invention, the test pattern to be applied to the inputs of the test unit (3) is constructed of sub-patterns, whose length is in particular