diff --git a/parsl/tests/integration/test_parsl_load_default_config.py b/parsl/tests/integration/test_parsl_load_default_config.py
index bb9446c4cd..bec81e693e 100644
--- a/parsl/tests/integration/test_parsl_load_default_config.py
+++ b/parsl/tests/integration/test_parsl_load_default_config.py
@@ -3,7 +3,7 @@
 
 
 @python_app
-def cpu_stress(inputs=[], outputs=[]):
+def cpu_stress(inputs=(), outputs=()):
     s = 0
     for i in range(10**8):
         s += i
diff --git a/parsl/tests/manual_tests/test_fan_in_out_htex_remote.py b/parsl/tests/manual_tests/test_fan_in_out_htex_remote.py
index 72dc4c7fd7..0b1d270de0 100644
--- a/parsl/tests/manual_tests/test_fan_in_out_htex_remote.py
+++ b/parsl/tests/manual_tests/test_fan_in_out_htex_remote.py
@@ -56,7 +56,7 @@ def inc(x):
 
 
 @python_app
-def add_inc(inputs=[]):
+def add_inc(inputs=()):
     import time
     start = time.time()
     sleep_duration = 30.0
diff --git a/parsl/tests/test_aalst_patterns.py b/parsl/tests/test_aalst_patterns.py
index 3e6311e350..71aa7c5654 100644
--- a/parsl/tests/test_aalst_patterns.py
+++ b/parsl/tests/test_aalst_patterns.py
@@ -77,7 +77,7 @@ def slow_increment(x, dur=1):
 
 
 @python_app
-def join(inputs=[]):
+def join(inputs=()):
     return sum(inputs)
 
 
@@ -96,7 +96,7 @@ def sleep_square(x):
 
 
 @python_app
-def sum_results(x=[]):
+def sum_results(x=()):
     total = 0
     for r in x:
         total += r.result()
@@ -109,12 +109,12 @@ def add(x, y):
 
 
 @python_app
-def sum_list(x=[]):
+def sum_list(x=()):
     return sum(x)
 
 
 @python_app
-def sum_lists(x=[], y=[], z=[]):
+def sum_lists(x=(), y=(), z=()):
     total = 0
     for i in range(len(x)):
         total += x[i].result()
@@ -126,7 +126,7 @@ def sum_lists(x=[], y=[], z=[]):
 
 
 @python_app
-def sum_elements(x=[], y=[], z=[]):
+def sum_elements(x=(), y=(), z=()):
     total = 0
     for i in range(len(x)):
         total += x[i].result()
diff --git a/parsl/tests/test_docs/test_from_slides.py b/parsl/tests/test_docs/test_from_slides.py
index 09f5e86f93..52be69b7b6 100644
--- a/parsl/tests/test_docs/test_from_slides.py
+++ b/parsl/tests/test_docs/test_from_slides.py
@@ -5,12 +5,12 @@
 
 
 @bash_app
-def echo(message, outputs=[]):
+def echo(message, outputs=()):
     return 'echo {m} &> {o}'.format(m=message, o=outputs[0])
 
 
 @python_app
-def cat(inputs=[]):
+def cat(inputs=()):
     with open(inputs[0].filepath) as f:
         return f.readlines()
 
diff --git a/parsl/tests/test_docs/test_tutorial_1.py b/parsl/tests/test_docs/test_tutorial_1.py
index 5f8906d4ca..6aab5dee85 100644
--- a/parsl/tests/test_docs/test_tutorial_1.py
+++ b/parsl/tests/test_docs/test_tutorial_1.py
@@ -11,7 +11,7 @@
 
 
 @bash_app
-def sim_mol_dyn(i, dur, outputs=[], stdout=None, stderr=None):
+def sim_mol_dyn(i, dur, outputs=(), stdout=None, stderr=None):
     # The bash app function, requires that the bash script is assigned to the special variable
     # cmd_line. Positional and Keyword args to the fn() are formatted into the cmd_line string
     cmd_line = """echo "{0}" > {outputs[0]}
diff --git a/parsl/tests/test_docs/test_workflow1.py b/parsl/tests/test_docs/test_workflow1.py
index 2678794a3c..f789a1ae62 100644
--- a/parsl/tests/test_docs/test_workflow1.py
+++ b/parsl/tests/test_docs/test_workflow1.py
@@ -18,7 +18,7 @@ def generate(limit):
 
 
 @bash_app
-def save(message, outputs=[]):
+def save(message, outputs=()):
     return 'echo {m} &> {o}'.format(m=message, o=outputs[0])
 
 
diff --git a/parsl/tests/test_error_handling/test_rand_fail.py b/parsl/tests/test_error_handling/test_rand_fail.py
index 50d58a500d..4b501b1daf 100644
--- a/parsl/tests/test_error_handling/test_rand_fail.py
+++ b/parsl/tests/test_error_handling/test_rand_fail.py
@@ -14,7 +14,7 @@ def local_config():
 
 
 @python_app
-def sleep_fail(sleep_dur, sleep_rand_max, fail_prob, inputs=[]):
+def sleep_fail(sleep_dur, sleep_rand_max, fail_prob, inputs=()):
     import time
     import random