[devscripts/run_tests] Use markers to filter tests (#1258)

`-k` filters using a substring match on test name.
`-m` checks markers for an exact match.
Authored by: sulyi

devscripts/run_tests.bat

@@ -3,11 +3,11 @@
 cd /d %~dp0..
 
 if ["%~1"]==[""] (
-    set "test_set="
+    set "test_set="test""
 ) else if ["%~1"]==["core"] (
-    set "test_set=-k "not download""
+    set "test_set="-m not download""
 ) else if ["%~1"]==["download"] (
-    set "test_set=-k download"
+    set "test_set="-m "download""
 ) else (
     echo.Invalid test type "%~1". Use "core" ^| "download"
     exit /b 1

devscripts/run_tests.sh

@@ -3,12 +3,12 @@
 if [ -z $1 ]; then
     test_set='test'
 elif [ $1 = 'core' ]; then
-    test_set='not download'
+    test_set="-m not download"
 elif [ $1 = 'download' ]; then
-    test_set='download'
+    test_set="-m download"
 else
     echo 'Invalid test type "'$1'". Use "core" | "download"'
     exit 1
 fi
 
-python3 -m pytest -k "$test_set"
+python3 -m pytest "$test_set"