add test method

README.md

@@ -20,6 +20,61 @@ make # cmake --build . is same
 ```
 
 ## run test
-```bash
-./build/test/run_tests
+### add your own test file on test/CMakeList.txt
+```
+set(TARGET_NAME run_tests)
+set(TEST_NAME test_test)
+
+# add test sources here ... 
+add_executable(${TARGET_NAME} 
+
+    ../lib/fischl.cpp 
+    testfischl.cpp
+    
+)
+add_executable(${TEST_NAME} 
+
+    ../lib/fischl.cpp 
+    testtest.cpp
+    
+)
+add_test(NAME ${TARGET_NAME} COMMAND ${TARGET_NAME})
+add_test(NAME ${TEST_NAME} COMMAND ${TEST_NAME})
+```
+
+### ctest
+```bash
+ctest -VVV 
+ctest -VV  #Displays the output from the tests (e.g., stdout or stderr) in addition to the test information.
+```
+Test Result will be like this
+```bash
+[cloud-user@ip-172-31-22-147 build]$ ctest -VVV
+Test project /home/cloud-user/iloveos/build
+    Start 1: run_tests
+1/1 Test #1: run_tests ........................   Passed    0.00 sec
+
+100% tests passed, 0 tests failed out of 1
+
+Total Test time (real) =   0.01 sec
+```
+
+Failed demonstration
+```bash
+[cloud-user@ip-172-31-22-147 build]$ ctest -VVV
+Test project /home/cloud-user/iloveos/build
+    Start 1: run_tests
+1/2 Test #1: run_tests ........................   Passed    0.00 sec
+    Start 2: test_test
+2/2 Test #2: test_test ........................Subprocess aborted***Exception:   0.26 sec
+
+50% tests passed, 1 tests failed out of 2
+
+Total Test time (real) =   0.27 sec
+
+The following tests FAILED:
+          2 - test_test (Subprocess aborted)
+Errors while running CTest
+Output from these tests are in: /home/cloud-user/iloveos/build/Testing/Temporary/LastTest.log
+Use "--rerun-failed --output-on-failure" to re-run the failed cases verbosely.
 ```