Remove --keep-going and reduce concurrency for CI on Windows (#14283)

Author: josevalim

.github/workflows/ci.yml

@@ -103,11 +103,11 @@ jobs:
       - name: Check format
         run: make test_formatted && echo "All Elixir source code files are properly formatted."
       - name: Erlang test suite
-        run: make --keep-going test_erlang
+        run: make test_erlang
       - name: Elixir test suite
         run: |
           Remove-Item 'c:/Windows/System32/drivers/etc/hosts'
-          make --keep-going test_elixir
+          make test_elixir
 
   check_posix_compliant:
     name: Check POSIX-compliant
@@ -125,7 +125,7 @@ jobs:
           shellcheck -e SC2039,2086 bin/elixir && echo "bin/elixir is POSIX compliant"
           shellcheck bin/elixirc && echo "bin/elixirc is POSIX compliant"
           shellcheck bin/iex && echo "bin/iex is POSIX compliant"
-  
+
   license_compliance:
     name: Check Licence Compliance
 
@@ -136,11 +136,11 @@ jobs:
         id: git-config
         shell: bash
         run: git config --global url.https://github.com/.insteadOf ssh://git@github.com/
-  
+
       - name: Checkout project
         id: checkout
         uses: actions/checkout@v4
-  
+
       - name: "Run OSS Review Toolkit"
         id: ort
         uses: ./.github/workflows/ort

lib/mix/test/test_helper.exs

@@ -49,7 +49,9 @@ cover_exclude =
 ExUnit.start(
   trace: !!System.get_env("TRACE"),
   exclude: epmd_exclude ++ os_exclude ++ git_exclude ++ line_exclude ++ cover_exclude,
-  include: line_include
+  include: line_include,
+  # Many mix tests spawns separate processes which leads to failures on Windows CI
+  max_cases: if(match?({:win32, _}, :os.type()), do: 1, else: System.schedulers_online() * 2)
 )
 
 # Clear environment variables that may affect tests