diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d5b25b2b5f..f587c62959 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -201,6 +201,16 @@ jobs:
       - name: Install Bundler RubyGems
         run: brew install-bundler-gems
 
+      - name: Create parallel test log directory
+        run: mkdir tests
+
+      - name: Cache parallel tests log
+        uses: actions/cache@v1
+        with:
+          path: tests
+          key: ${{ runner.os }}-${{ matrix.test-flags }}-parallel_runtime_rspec-${{ github.sha }}
+          restore-keys: ${{ runner.os }}-${{ matrix.test-flags }}-parallel_runtime_rspec-
+
       - name: Run brew tests
         run: |
           # brew tests doesn't like world writable directories
@@ -283,6 +293,16 @@ jobs:
           which svn
           which svnadmin
 
+      - name: Create parallel test log directory
+        run: mkdir tests
+
+      - name: Cache parallel tests log
+        uses: actions/cache@v1
+        with:
+          path: tests
+          key: ${{ runner.os }}-parallel_runtime_rspec-${{ github.sha }}
+          restore-keys: ${{ runner.os }}-parallel_runtime_rspec-
+
       - name: Run brew tests
         run: brew tests --online --coverage
         env:
diff --git a/Library/Homebrew/dev-cmd/tests.rb b/Library/Homebrew/dev-cmd/tests.rb
index 259f7a45c7..4900b0ef8d 100644
--- a/Library/Homebrew/dev-cmd/tests.rb
+++ b/Library/Homebrew/dev-cmd/tests.rb
@@ -98,10 +98,23 @@ module Homebrew
         Dir.glob("test/**/*_spec.rb")
       end
 
+      parallel_rspec_log_name = "parallel_runtime_rspec"
+      parallel_rspec_log_name = "#{parallel_rspec_log_name}.no_compat" if args.no_compat?
+      parallel_rspec_log_name = "#{parallel_rspec_log_name}.generic" if args.generic?
+      parallel_rspec_log_name = "#{parallel_rspec_log_name}.online" if args.online?
+      parallel_rspec_log_name = "#{parallel_rspec_log_name}.log"
+
+      parallel_rspec_log_path = if ENV["CI"]
+        "tests/#{parallel_rspec_log_name}"
+      else
+        "#{HOMEBREW_CACHE}/#{parallel_rspec_log_name}"
+      end
+
       parallel_args = if ENV["CI"]
-        %w[
+        %W[
           --combine-stderr
           --serialize-stdout
+          --runtime-log "#{parallel_rspec_log_path}"
         ]
       else
         %w[
@@ -120,7 +133,7 @@ module Homebrew
         --require spec_helper
         --format NoSeedProgressFormatter
         --format ParallelTests::RSpec::RuntimeLogger
-        --out #{HOMEBREW_CACHE}/tests/parallel_runtime_rspec.log
+        --out #{parallel_rspec_log_path}
       ]
 
       bundle_args << "--format" << "RSpec::Github::Formatter" if ENV["GITHUB_ACTIONS"]