diff --git a/.gitignore b/.gitignore
index ee460538..9b49d549 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,13 +7,18 @@
 .ipynb_checkpoints
 
 /test/kernel
-/test/shape/*.obj
-
-/test/TPM_Ryugu
-/test/non-uniform_thermoparams
-/test/TPM_Didymos
+/test/shape/*
 
 # Keep these shape models
-!/test/shape/icosahedron.obj
-!/test/shape/single_face.obj
-!/test/shape/ryugu_test.obj
+!icosahedron.obj
+!single_face.obj
+!ryugu_test.obj
+
+/test/TPM_Ryugu/*
+/test/TPM_non-uniform_thermoparams/*
+/test/TPM_Didymos/*
+
+# Keep these test files
+!TPM_Ryugu.jl
+!TPM_non-uniform_thermoparams.jl
+!TPM_Didymos.jl
diff --git a/src/TPM.jl b/src/TPM.jl
index 7effbb5a..dbc18d12 100644
--- a/src/TPM.jl
+++ b/src/TPM.jl
@@ -394,10 +394,16 @@ end
 """
     export_TPM_results(dirpath, result::SingleTPMResult)
 
-Export the result of `SingleTPM` to CSV files.
+Export the result of `SingleTPM` to CSV files. 
+The output files are saved in the following directory structure:
+
+    dirpath
+    ├── physical_quantities.csv
+    ├── subsurface_temperature.csv
+    └── surface_temperature.csv
 
 # Arguments
-- `dirpath` :  Path to the directory to save CSV files
+- `dirpath` : Path to the directory to save CSV files.
 - `result`  : Output data format for `SingleTPM`
 """
 function export_TPM_results(dirpath, result::SingleTPMResult)
@@ -452,12 +458,23 @@ end
 
 
 """
-    export_TPM_results(filepath, result::BinaryTPMResult)
+    export_TPM_results(dirpath, result::BinaryTPMResult)
+
+Export the result of `BinaryTPM` to CSV files. 
+The output files are saved in the following directory structure:
 
-Export the result of `BinaryTPM` to CSV files.
+    dirpath
+    ├── pri
+    │   ├── physical_quantities.csv
+    │   ├── subsurface_temperature.csv
+    │   └── surface_temperature.csv
+    └── sec
+        ├── physical_quantities.csv
+        ├── subsurface_temperature.csv
+        └── surface_temperature.csv
 
 # Arguments
-- `dirpath` : Path to the directory to save CSV files
+- `dirpath` : Path to the directory to save CSV files.
 - `result`  : Output data format for `BinaryTPM`
 """
 function export_TPM_results(dirpath, result::BinaryTPMResult)
diff --git a/test/TPM_Didymos.jl b/test/TPM_Didymos/TPM_Didymos.jl
similarity index 98%
rename from test/TPM_Didymos.jl
rename to test/TPM_Didymos/TPM_Didymos.jl
index 3ca75320..99a3d232 100644
--- a/test/TPM_Didymos.jl
+++ b/test/TPM_Didymos/TPM_Didymos.jl
@@ -146,7 +146,6 @@
     result = AsteroidThermoPhysicalModels.run_TPM!(btpm, ephem, times_to_save, face_ID_pri, face_ID_sec)
 
     ##= Save TPM result =##
-    savedir = "TPM_Didymos"
-    mkpath(savedir)
-    AsteroidThermoPhysicalModels.export_TPM_results(savedir, result)
+    dirpath = "./TPM_Didymos"
+    AsteroidThermoPhysicalModels.export_TPM_results(dirpath, result)
 end
diff --git a/test/TPM_Ryugu.jl b/test/TPM_Ryugu/TPM_Ryugu.jl
similarity index 97%
rename from test/TPM_Ryugu.jl
rename to test/TPM_Ryugu/TPM_Ryugu.jl
index 0307f2f4..14b312a1 100644
--- a/test/TPM_Ryugu.jl
+++ b/test/TPM_Ryugu/TPM_Ryugu.jl
@@ -103,7 +103,6 @@
     result = AsteroidThermoPhysicalModels.run_TPM!(stpm, ephem, times_to_save, face_ID)
     
     ##= Save TPM result =##
-    savedir = "TPM_Ryugu"
-    mkpath(savedir)
-    AsteroidThermoPhysicalModels.export_TPM_results(savedir, result)
+    dirpath = "./TPM_Ryugu"
+    AsteroidThermoPhysicalModels.export_TPM_results(dirpath, result)
 end
diff --git a/test/non-uniform_thermoparams.jl b/test/TPM_non-uniform_thermoparams/TPM_non-uniform_thermoparams.jl
similarity index 96%
rename from test/non-uniform_thermoparams.jl
rename to test/TPM_non-uniform_thermoparams/TPM_non-uniform_thermoparams.jl
index ee32911e..080af28f 100644
--- a/test/non-uniform_thermoparams.jl
+++ b/test/TPM_non-uniform_thermoparams/TPM_non-uniform_thermoparams.jl
@@ -115,8 +115,7 @@
 
     result = AsteroidThermoPhysicalModels.run_TPM!(stpm, ephem, times_to_save, face_ID)
 
-    ##= Save TPM result =##'
-    savedir = "non-uniform_thermoparams"
-    mkpath(savedir)
-    AsteroidThermoPhysicalModels.export_TPM_results(savedir, result)
+    ##= Save TPM result =##
+    dirpath = "./TPM_non-uniform_thermoparams"
+    AsteroidThermoPhysicalModels.export_TPM_results(dirpath, result)
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index b1df0ad0..1e1049eb 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -13,7 +13,7 @@ using DataFrames
 Aqua.test_all(AsteroidThermoPhysicalModels, ambiguities=false)
 
 include("find_visiblefacets.jl")
-include("TPM_Ryugu.jl")
-include("non-uniform_thermoparams.jl")
-include("TPM_Didymos.jl")
+include("TPM_Ryugu/TPM_Ryugu.jl")
+include("TPM_non-uniform_thermoparams/TPM_non-uniform_thermoparams.jl")
+include("TPM_Didymos/TPM_Didymos.jl")
 include("heat_conduction_1D.jl")