chore: setup for parallelizing unit tests across Python versions

PiperOrigin-RevId: 566304233

Author: sararob

.kokoro/presubmit/presubmit.cfg

@@ -1,6 +1,7 @@
 # Format: //devtools/kokoro/config/proto/build.proto
 
 # Run all sessions except system tests and docs builds
+# TODO(sararob): update this to unit-3.8 and change in noxfile.py after cl/565663310 is submitted
 env_vars: {
     key: "NOX_SESSION"
     value: "unit lint lint_setup_py blacken cover"

.kokoro/presubmit/unit_3-10.cfg

@@ -0,0 +1,13 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Run unit tests for Python 3.10
+env_vars: {
+    key: "NOX_SESSION"
+    value: "unit-3.10"
+}
+
+# Run unit tests in parallel, splitting up by file
+env_vars: {
+    key: "PYTEST_ADDOPTS"
+    value: "-n=auto --dist=loadscope"
+}

.kokoro/presubmit/unit_3-11.cfg

@@ -0,0 +1,13 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Run unit tests for Python 3.11
+env_vars: {
+    key: "NOX_SESSION"
+    value: "unit-3.11"
+}
+
+# Run unit tests in parallel, splitting up by file
+env_vars: {
+    key: "PYTEST_ADDOPTS"
+    value: "-n=auto --dist=loadscope"
+}

.kokoro/presubmit/unit_3-8.cfg

@@ -0,0 +1,13 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Run unit tests for Python 3.8
+env_vars: {
+    key: "NOX_SESSION"
+    value: "unit-3.8"
+}
+
+# Run unit tests in parallel, splitting up by file
+env_vars: {
+    key: "PYTEST_ADDOPTS"
+    value: "-n=auto --dist=loadscope"
+}

.kokoro/presubmit/unit_3-9.cfg

@@ -0,0 +1,13 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Run unit tests for Python 3.9
+env_vars: {
+    key: "NOX_SESSION"
+    value: "unit-3.9"
+}
+
+# Run unit tests in parallel, splitting up by file
+env_vars: {
+    key: "PYTEST_ADDOPTS"
+    value: "-n=auto --dist=loadscope"
+}