diff --git a/bilby_pipe/input.py b/bilby_pipe/input.py
index 4a1906c291d8fcba42ecd353bbe0d04875905252..1d57f7620940ae23ab69af0ca13f17c22545673a 100644
--- a/bilby_pipe/input.py
+++ b/bilby_pipe/input.py
@@ -1046,7 +1046,7 @@ class Input(object):
                 self, "likelihood_lookup_table"
             )
 
-        if self.likelihood_type == "GravitationalWaveTransient":
+        if self.likelihood_type in ["GravitationalWaveTransient", "zero"]:
             Likelihood = bilby.gw.likelihood.GravitationalWaveTransient
             likelihood_kwargs.update(jitter_time=self.jitter_time)
 
@@ -1085,7 +1085,14 @@ class Input(object):
             f"Initialise likelihood {Likelihood} with kwargs: \n{likelihood_kwargs}"
         )
 
-        return Likelihood(**likelihood_kwargs)
+        likelihood = Likelihood(**likelihood_kwargs)
+
+        # If requested, use a zero likelihood: for testing purposes
+        if self.likelihood_type == "zero":
+            logger.info("Using a ZeroLikelihood")
+            likelihood = bilby.core.likelihood.ZeroLikelihood(likelihood)
+
+        return likelihood
 
     @property
     def extra_likelihood_kwargs(self):
diff --git a/bilby_pipe/parser.py b/bilby_pipe/parser.py
index 1157f55ebf4725acc1493cd90cab243987c0c6b6..875a716dd448fd9895da84a8fb94f9288ee2b094 100644
--- a/bilby_pipe/parser.py
+++ b/bilby_pipe/parser.py
@@ -618,9 +618,12 @@ def create_parser(top_level=True):
         default="GravitationalWaveTransient",
         help=(
             "The likelihood. Can be one of [GravitationalWaveTransient, "
-            "ROQGravitationalWaveTransient] or python path to a bilby "
+            "ROQGravitationalWaveTransient, zero] or python path to a bilby "
             "likelihood class available in the users installation. "
-            "Need to specify --roq-folder if ROQ likelihood used"
+            "The --roq-folder is required if the ROQ likelihood used."
+            "The --roq-folder is required if the ROQ likelihood used."
+            "If `zero` is given, a testing ZeroLikelihood is used which always"
+            "return zero."
         ),
     )
     likelihood_parser.add(