tf.keras.backend.in_test_phase

Selects x in test phase, and alt otherwise.

Note that alt should have the same shape as x.

x What to return in test phase (tensor or callable that returns a tensor).
alt What to return otherwise (tensor or callable that returns a tensor).
training Optional scalar tensor (or Python boolean, or Python integer) specifying the learning phase.

Either x or alt based on K.learning_phase.