diff --git a/fslstats.cc b/fslstats.cc
index 8e90fd22080a2e5a0917f1cccbf5eba447e2b46e..b29d9f934a274dd6ea98fb081eb499897d1c0c4b 100644
--- a/fslstats.cc
+++ b/fslstats.cc
@@ -199,11 +199,9 @@ int fmrib_main_float(int argc, char *argv[], const bool timeseriesMode, const st
         generateNonZeroMask(mask, masknz, vol);
       }
       int narg(2);
-      bool last = false;
       while (narg < argc)
       {
 
-        last = !(narg < argc - 1);
         string sarg(argv[narg]);
         if (sarg == "-n")
         {
diff --git a/tests/fslstats/feedsRun b/tests/fslstats/feedsRun
index a007f1dd74c02c6dcb61231246aa462a4af03f61..8e722db837e9a841e625dec2988cdc53e6b8505a 100755
--- a/tests/fslstats/feedsRun
+++ b/tests/fslstats/feedsRun
@@ -46,31 +46,31 @@ import nibabel as nib
 np.random.seed(0)
 
 options = [
-    {"option": "-r", "expected": "0.018533 0.978824"},
-    {"option": "-R", "expected": "0.000546 0.999809"},
-    {"option": "-e", "expected": "0.906103"},
-    {"option": "-E", "expected": "0.906103"},
-    {"option": "-v", "expected": "1000 1000.000000"},
-    {"option": "-V", "expected": "1000 1000.000000"},
-    {"option": "-m", "expected": "0.495922"},
-    {"option": "-m -a", "expected": "0.495922"},
-    {"option": "-m -a -n", "expected": "0.495922"},
-    {"option": "-M", "expected": "0.495922"},
-    {"option": "-s", "expected": "0.290744"},
-    {"option": "-S", "expected": "0.290744"},
-    {"option": "-w", "expected": "0 10 0 10 0 10 0 1"},
-    {"option": "-x", "expected": "9 7 4"},
-    {"option": "-X", "expected": "8 2 1"},
-    {"option": "-c", "expected": "4.498706 4.545873 4.613188"},
-    {"option": "-C", "expected": "4.498706 4.545873 4.613188"},
-    {"option": "-p 50", "expected": "0.482584"},
-    {"option": "-P 50", "expected": "0.482584"},
-    {"option": "-m -h 10 -c", "expected": "0.495922 101.000000 \n99.000000 \n108.000000 \n107.000000 \n102.000000 \n93.000000 \n99.000000 \n88.000000 \n95.000000 \n108.000000 \n 4.498706 4.545873 4.613188"},
-    {"option": "-m -h 10", "expected": "0.495922 101.000000 \n99.000000 \n108.000000 \n107.000000 \n102.000000 \n93.000000 \n99.000000 \n88.000000 \n95.000000 \n108.000000"},
-    {"option": "-h 10", "expected": "101.000000 \n99.000000 \n108.000000 \n107.000000 \n102.000000 \n93.000000 \n99.000000 \n88.000000 \n95.000000 \n108.000000"},
-    {"option": "-H 10 0 1", "expected": "98.000000 \n102.000000 \n107.000000 \n108.000000 \n102.000000 \n93.000000 \n99.000000 \n88.000000 \n95.000000 \n108.000000"},
-    {"option": "-l 0.25 -u 0.75 -m", "expected": "0.495150"},
-    {"option": "-d imageForDiff.nii.gz -m", "expected": "0.000000"},
+    {"name": "robust", "option": "-r", "expected": "0.018533 0.978824"},
+    {"name": "notRobust", "option": "-R", "expected": "0.000546 0.999809"},
+    {"name": "entropy", "option": "-e", "expected": "0.906103"},
+    {"name": "entropyNonzero", "option": "-E", "expected": "0.906103"},
+    {"name": "volume", "option": "-v", "expected": "1000 1000.000000"},
+    {"name": "volumeNonzero", "option": "-V", "expected": "1000 1000.000000"},
+    {"name": "mean", "option": "-m", "expected": "0.495922"},
+    {"name": "mean", "option": "-m -a", "expected": "0.495922"},
+    {"name": "mean", "option": "-m -a -n", "expected": "0.495922"},
+    {"name": "meanNonzero", "option": "-M", "expected": "0.495922"},
+    {"name": "stdev", "option": "-s", "expected": "0.290744"},
+    {"name": "stdevNonzero", "option": "-S", "expected": "0.290744"},
+    {"name": "roi","option": "-w", "expected": "0 10 0 10 0 10 0 1"},
+    {"name": "maxCoord", "option": "-x", "expected": "9 7 4"},
+    {"name": "minCoord", "option": "-X", "expected": "8 2 1"},
+    {"name": "cogMM", "option": "-c", "expected": "4.498706 4.545873 4.613188"},
+    {"name": "cogVox","option": "-C", "expected": "4.498706 4.545873 4.613188"},
+    {"name": "percentile", "option": "-p 50", "expected": "0.482584"},
+    {"name": "percentileNonzero","option": "-P 50", "expected": "0.482584"},
+    {"name": "meanHistCog", "option": "-m -h 10 -c", "expected": "0.495922 101.000000 \n99.000000 \n108.000000 \n107.000000 \n102.000000 \n93.000000 \n99.000000 \n88.000000 \n95.000000 \n108.000000 \n 4.498706 4.545873 4.613188"},
+    {"name": "meanHist", "option": "-m -h 10", "expected": "0.495922 101.000000 \n99.000000 \n108.000000 \n107.000000 \n102.000000 \n93.000000 \n99.000000 \n88.000000 \n95.000000 \n108.000000"},
+    {"name": "hist", "option": "-h 10", "expected": "101.000000 \n99.000000 \n108.000000 \n107.000000 \n102.000000 \n93.000000 \n99.000000 \n88.000000 \n95.000000 \n108.000000"},
+    {"name": "histLimits", "option": "-H 10 0 1", "expected": "98.000000 \n102.000000 \n107.000000 \n108.000000 \n102.000000 \n93.000000 \n99.000000 \n88.000000 \n95.000000 \n108.000000"},
+    {"name": "threshold", "option": "-l 0.25 -u 0.75 -m", "expected": "0.495150"},
+    {"name": "diff", "option": "-d imageForDiff.nii.gz -m", "expected": "0.000000"},
 ]
 
 # create a list of tests and expected results
@@ -82,6 +82,7 @@ for option in options:
             "mask": "",
             "options": option["option"],
             "expected": option["expected"],
+            "name": option["name"],
         }
     )
 
@@ -91,21 +92,49 @@ tests_with_preoptions = [
         "mask": "mask.nii.gz",
         "options": "-m",
         "expected": "1.078044 \n1.028827 \n0.986428 \n1.020869",
+        "name": "preopIndexMaskMean",
     },
     {
         "preoptions": "-t -K",
         "mask": "mask.nii.gz",
         "options": "-m",
         "expected": "0.526682 \n0.515652 \n0.492337 \n0.511661 \n0.551362 \n0.513176 \n0.494091 \n0.509208",
+        "name": "preopIndexMaskMeanTimeSeries",
     },
     {
         "preoptions": "-t",
         "mask": "",
         "options": "-m",
         "expected": "0.503236 \n0.504035",
+        "name": "preopMeanTimeSeries",
     },
 ]
 
+json_tests = []
+for option in options:
+    file_string = f"test_{option['name']}_{option['option'].replace(' ', '_')}.json"
+    file_string = file_string.replace("-", "")
+    json_tests.append(
+        {
+            "preoptions": "",
+            "mask": "",
+            "options": option["option"],
+            "expected": file_string,
+        }
+    )
+
+for option in tests_with_preoptions:
+    file_string = f"test_{option['name']}_{option['preoptions'].replace(' ', '_')}_{option['options'].replace(' ', '_')}.json"
+    file_string = file_string.replace("-", "")
+    json_tests.append(
+        {
+            "preoptions": option["preoptions"],
+            "mask": option["mask"],
+            "options": option["options"],
+            "expected": file_string,
+        }
+    )
+
 def test_fslstats():
     imgfile = 'test.nii.gz'
 
@@ -121,8 +150,11 @@ def test_fslstats():
         try:
             assert output == test["expected"]
         except AssertionError:
+            print('Failed test')
             print(cmd)
+            print('Output')
             print(output)
+            print('Expected')
             print(test["expected"])
             raise
 
@@ -147,6 +179,37 @@ def test_fslstats():
             print(test["expected"])
             raise
 
+    # run the json tests
+    for test in json_tests:
+        cmd = f"fslstats -json {test['preoptions']} {test['mask']} {imgfile} {test['options']}"
+        # remove any double spaces from empty test options
+        cmd = " ".join(cmd.split())
+        print(cmd, flush=True)
+        output = run.runfsl(cmd)
+
+        # try to load the expected json file
+        # if it exists, compare the output to the expected
+        try:
+            print(test["expected"])
+            with open(test["expected"], "r") as json_file:
+                # read the file as a string
+                expected = json_file.read()
+                try:
+                    assert output == expected    
+                except AssertionError:
+                    print('Failed test')
+                    print(cmd)
+                    print('Output')
+                    print(output)
+                    print('Expected')
+                    print(expected)
+                    raise
+        except FileNotFoundError:
+            # if the expected json file doesn't exist, create it from the output
+            # usefull for creating new tests or the first time a test is run
+            with open(test["expected"], "w") as json_file:
+                json_file.write(output)
+
 
 if __name__ == "__main__":
     test_fslstats()
diff --git a/tests/fslstats/test_cogMM_c.json b/tests/fslstats/test_cogMM_c.json
new file mode 100644
index 0000000000000000000000000000000000000000..758ec3c4ea87958f2b46bc64f2c2c4b4cc53a91a
--- /dev/null
+++ b/tests/fslstats/test_cogMM_c.json
@@ -0,0 +1,15 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-c": [
+                        4.505939956803816,
+                        4.486097425091172,
+                        4.488288600081377
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_cogVox_C.json b/tests/fslstats/test_cogVox_C.json
new file mode 100644
index 0000000000000000000000000000000000000000..1b6b7b0042df12032ef3fba38c5279efd005e671
--- /dev/null
+++ b/tests/fslstats/test_cogVox_C.json
@@ -0,0 +1,15 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-C": [
+                        4.505939956803816,
+                        4.486097425091172,
+                        4.488288600081377
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_diff_d_imageForDiff.nii.gz_m.json b/tests/fslstats/test_diff_d_imageForDiff.nii.gz_m.json
new file mode 100644
index 0000000000000000000000000000000000000000..76d250a99ba24c780ad8177fbd3f31c5cbc82767
--- /dev/null
+++ b/tests/fslstats/test_diff_d_imageForDiff.nii.gz_m.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-m": 0.0077142266542650755
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_entropyNonzero_E.json b/tests/fslstats/test_entropyNonzero_E.json
new file mode 100644
index 0000000000000000000000000000000000000000..9573a6e2e3ea79b23560e254157c2d15a12dfff5
--- /dev/null
+++ b/tests/fslstats/test_entropyNonzero_E.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-E": 0.9468094676591793
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_entropy_e.json b/tests/fslstats/test_entropy_e.json
new file mode 100644
index 0000000000000000000000000000000000000000..407d1864d013c94088173ee18a6cca522b736898
--- /dev/null
+++ b/tests/fslstats/test_entropy_e.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-e": 0.9468094676591793
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_histLimits_H_10_0_1.json b/tests/fslstats/test_histLimits_H_10_0_1.json
new file mode 100644
index 0000000000000000000000000000000000000000..4ce81ec78aa6c653dcdec7d31c72c7d604b95fd4
--- /dev/null
+++ b/tests/fslstats/test_histLimits_H_10_0_1.json
@@ -0,0 +1,22 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-H": [
+                        193.0,
+                        220.0,
+                        194.0,
+                        201.0,
+                        190.0,
+                        184.0,
+                        191.0,
+                        199.0,
+                        200.0,
+                        228.0
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_hist_h_10.json b/tests/fslstats/test_hist_h_10.json
new file mode 100644
index 0000000000000000000000000000000000000000..2e210d2ba04254ede95cb789bb3e6f50b807a412
--- /dev/null
+++ b/tests/fslstats/test_hist_h_10.json
@@ -0,0 +1,22 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-h": [
+                        198.0,
+                        216.0,
+                        194.0,
+                        200.0,
+                        190.0,
+                        184.0,
+                        191.0,
+                        199.0,
+                        199.0,
+                        229.0
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_maxCoord_x.json b/tests/fslstats/test_maxCoord_x.json
new file mode 100644
index 0000000000000000000000000000000000000000..1a2017282d339384c75ffb8cba333700341fdad7
--- /dev/null
+++ b/tests/fslstats/test_maxCoord_x.json
@@ -0,0 +1,15 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-x": [
+                        4,
+                        8,
+                        7
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_meanHistCog_m_h_10_c.json b/tests/fslstats/test_meanHistCog_m_h_10_c.json
new file mode 100644
index 0000000000000000000000000000000000000000..58380fdb02573fc29b8dded4ae7edd8f7a3c8701
--- /dev/null
+++ b/tests/fslstats/test_meanHistCog_m_h_10_c.json
@@ -0,0 +1,28 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-c": [
+                        4.505939956803816,
+                        4.486097425091172,
+                        4.488288600081377
+                    ],
+                    "-h": [
+                        198.0,
+                        216.0,
+                        194.0,
+                        200.0,
+                        190.0,
+                        184.0,
+                        191.0,
+                        199.0,
+                        199.0,
+                        229.0
+                    ],
+                    "-m": 0.5036357601464115
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_meanHist_m_h_10.json b/tests/fslstats/test_meanHist_m_h_10.json
new file mode 100644
index 0000000000000000000000000000000000000000..c8316e5e320510f9a8d269ea71760ffa426277c4
--- /dev/null
+++ b/tests/fslstats/test_meanHist_m_h_10.json
@@ -0,0 +1,23 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-h": [
+                        198.0,
+                        216.0,
+                        194.0,
+                        200.0,
+                        190.0,
+                        184.0,
+                        191.0,
+                        199.0,
+                        199.0,
+                        229.0
+                    ],
+                    "-m": 0.5036357601464115
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_meanNonzero_M.json b/tests/fslstats/test_meanNonzero_M.json
new file mode 100644
index 0000000000000000000000000000000000000000..e7892ba4cd9fdd18868824b58ea99ed18f3cc330
--- /dev/null
+++ b/tests/fslstats/test_meanNonzero_M.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-M": 0.5036357601464115
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_mean_m.json b/tests/fslstats/test_mean_m.json
new file mode 100644
index 0000000000000000000000000000000000000000..3763ba8a708cddda21719ed8afdd6df152158fdd
--- /dev/null
+++ b/tests/fslstats/test_mean_m.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-m": 0.5036357601464115
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_mean_m_a.json b/tests/fslstats/test_mean_m_a.json
new file mode 100644
index 0000000000000000000000000000000000000000..3763ba8a708cddda21719ed8afdd6df152158fdd
--- /dev/null
+++ b/tests/fslstats/test_mean_m_a.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-m": 0.5036357601464115
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_mean_m_a_n.json b/tests/fslstats/test_mean_m_a_n.json
new file mode 100644
index 0000000000000000000000000000000000000000..3763ba8a708cddda21719ed8afdd6df152158fdd
--- /dev/null
+++ b/tests/fslstats/test_mean_m_a_n.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-m": 0.5036357601464115
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_minCoord_X.json b/tests/fslstats/test_minCoord_X.json
new file mode 100644
index 0000000000000000000000000000000000000000..aa72b2ef8e9255249a9e19a6ffa9fc1c0ed2870d
--- /dev/null
+++ b/tests/fslstats/test_minCoord_X.json
@@ -0,0 +1,15 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-X": [
+                        8,
+                        1,
+                        6
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_notRobust_R.json b/tests/fslstats/test_notRobust_R.json
new file mode 100644
index 0000000000000000000000000000000000000000..b5b7acd3e86b3f8de0302bcdc47f6ca7453a63dd
--- /dev/null
+++ b/tests/fslstats/test_notRobust_R.json
@@ -0,0 +1,14 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-R": [
+                        0.00036734374589286745,
+                        0.9998085498809814
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_percentileNonzero_P_50.json b/tests/fslstats/test_percentileNonzero_P_50.json
new file mode 100644
index 0000000000000000000000000000000000000000..47aeceb4aa12b07fd9f9d94fc334e32df0da3c83
--- /dev/null
+++ b/tests/fslstats/test_percentileNonzero_P_50.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-P": 0.5013243556022644
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_percentile_p_50.json b/tests/fslstats/test_percentile_p_50.json
new file mode 100644
index 0000000000000000000000000000000000000000..a105e7c94c23eb9c88bce4dd7f1c4be225ab2924
--- /dev/null
+++ b/tests/fslstats/test_percentile_p_50.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-p": 0.5013243556022644
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_preopIndexMaskMeanTimeSeries_t_K_m.json b/tests/fslstats/test_preopIndexMaskMeanTimeSeries_t_K_m.json
new file mode 100644
index 0000000000000000000000000000000000000000..9f0e754f72c2f899b2d531512c8dd4294a6b4822
--- /dev/null
+++ b/tests/fslstats/test_preopIndexMaskMeanTimeSeries_t_K_m.json
@@ -0,0 +1,36 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-m": 0.5266819608311916
+                },
+                {
+                    "-m": 0.5156517274568186
+                },
+                {
+                    "-m": 0.49233699466459285
+                },
+                {
+                    "-m": 0.5116614613561304
+                }
+            ]
+        },
+        {
+            "indices": [
+                {
+                    "-m": 0.5513619920395724
+                },
+                {
+                    "-m": 0.5131755568141885
+                },
+                {
+                    "-m": 0.49409089087108476
+                },
+                {
+                    "-m": 0.5092079986783641
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_preopIndexMaskMean_K_m.json b/tests/fslstats/test_preopIndexMaskMean_K_m.json
new file mode 100644
index 0000000000000000000000000000000000000000..fd62a2f93b208692544c6a564450f7913aa16133
--- /dev/null
+++ b/tests/fslstats/test_preopIndexMaskMean_K_m.json
@@ -0,0 +1,20 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-m": 1.078043952870764
+                },
+                {
+                    "-m": 1.0288272842710071
+                },
+                {
+                    "-m": 0.9864278855356776
+                },
+                {
+                    "-m": 1.0208694600344945
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_preopMeanTimeSeries_t_m.json b/tests/fslstats/test_preopMeanTimeSeries_t_m.json
new file mode 100644
index 0000000000000000000000000000000000000000..b2b481f0415c2d2ae1060aaa139593ce3b1db9fe
--- /dev/null
+++ b/tests/fslstats/test_preopMeanTimeSeries_t_m.json
@@ -0,0 +1,18 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-m": 0.503236498022452
+                }
+            ]
+        },
+        {
+            "indices": [
+                {
+                    "-m": 0.504035022270371
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_robust_r.json b/tests/fslstats/test_robust_r.json
new file mode 100644
index 0000000000000000000000000000000000000000..9810ac1677f1508fa2a4fb09a4e53c2da26217c6
--- /dev/null
+++ b/tests/fslstats/test_robust_r.json
@@ -0,0 +1,14 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-r": [
+                        0.018357284367084503,
+                        0.982818067073822
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_roi_w.json b/tests/fslstats/test_roi_w.json
new file mode 100644
index 0000000000000000000000000000000000000000..d023769141f6bc830c86436e7d26d730e69e1074
--- /dev/null
+++ b/tests/fslstats/test_roi_w.json
@@ -0,0 +1,20 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-w": [
+                        0,
+                        10,
+                        0,
+                        10,
+                        0,
+                        10,
+                        0,
+                        2
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_stdevNonzero_S.json b/tests/fslstats/test_stdevNonzero_S.json
new file mode 100644
index 0000000000000000000000000000000000000000..cdb0547b2196d2c346452c752aca43fd0e581c37
--- /dev/null
+++ b/tests/fslstats/test_stdevNonzero_S.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-S": 0.2949828225878523
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_stdev_s.json b/tests/fslstats/test_stdev_s.json
new file mode 100644
index 0000000000000000000000000000000000000000..b473581a8be07219141475c501720b8a2f605684
--- /dev/null
+++ b/tests/fslstats/test_stdev_s.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-s": 0.29498282199940035
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_threshold_l_0.25_u_0.75_m.json b/tests/fslstats/test_threshold_l_0.25_u_0.75_m.json
new file mode 100644
index 0000000000000000000000000000000000000000..6712e13e07ae3d558abd26e1e223374c7fdf754c
--- /dev/null
+++ b/tests/fslstats/test_threshold_l_0.25_u_0.75_m.json
@@ -0,0 +1,11 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-m": 0.49646345829352356
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_volumeNonzero_V.json b/tests/fslstats/test_volumeNonzero_V.json
new file mode 100644
index 0000000000000000000000000000000000000000..9a1ed332a56087d76f6d4a1d414828c2b64dc003
--- /dev/null
+++ b/tests/fslstats/test_volumeNonzero_V.json
@@ -0,0 +1,14 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-V": [
+                        2000.0,
+                        2000.0
+                    ]
+                }
+            ]
+        }
+    ]
+}
diff --git a/tests/fslstats/test_volume_v.json b/tests/fslstats/test_volume_v.json
new file mode 100644
index 0000000000000000000000000000000000000000..5e4fb299ead33a17ff8540d8d425fbaca09972cc
--- /dev/null
+++ b/tests/fslstats/test_volume_v.json
@@ -0,0 +1,14 @@
+{
+    "volumes": [
+        {
+            "indices": [
+                {
+                    "-v": [
+                        2000.0,
+                        2000.0
+                    ]
+                }
+            ]
+        }
+    ]
+}