diff --git a/build.sh b/build.sh
index 2f0595e..ca651fb 100755
--- a/build.sh
+++ b/build.sh
@@ -18,9 +18,9 @@ set -euo pipefail
 
 # Actions
 benchmark=0 # Should run benchmarks?
-build=1 # Should build images?
-library_tests=0 # Should try to install top N Python libraries
+build=0 # Should build images?
 system_tests=0 # Should run system tests?
+tests=0 # Should run standard test suite?
 
 local=0 # Should run using local Docker daemon instead of GCR?
 
@@ -40,32 +40,37 @@ Build and test artifacts in this repository
 
 Options:
   --[no]benchmark: Run benchmarking suite (default false)
-  --[no]build: Build all images (default true)
-  --[no]library_tests: Run library compatiblity tests (default false)
+  --[no]build: Build all images (default true if no options set)
+  --[no]tests: Run basic tests (default true if no options set)
   --[no]local: Build images using local Docker daemon (default false)
   --[no]system_tests: Run system tests (default false)
 "
 }
-  
+
 # Read environment variables
-if [ -z "${DOCKER_NAMESPACE+set}" ] ; then
+if [ -z "${DOCKER_NAMESPACE:+set}" ] ; then
   fatal 'Error: $DOCKER_NAMESPACE is not set; invoke with something like DOCKER_NAMESPACE=gcr.io/YOUR-PROJECT-NAME'
 fi
 
-if [ -z "${BUILDER_DOCKER_NAMESPACE+set}" ] ; then
+if [ -z "${BUILDER_DOCKER_NAMESPACE:+set}" ] ; then
   export BUILDER_DOCKER_NAMESPACE="${DOCKER_NAMESPACE}"
 fi
 
-if [ -z "${TAG+set}" ] ; then
+if [ -z "${TAG:+set}" ] ; then
   export TAG=`date +%Y-%m-%d-%H%M%S`
 fi
 
-substitutions="\
+build_substitutions="\
 _BUILDER_DOCKER_NAMESPACE=${BUILDER_DOCKER_NAMESPACE},\
 _DOCKER_NAMESPACE=${DOCKER_NAMESPACE},\
 _TAG=${TAG}\
 "
 
+substitutions="\
+_DOCKER_NAMESPACE=${DOCKER_NAMESPACE},\
+_TAG=${TAG}\
+"
+
 # Read command line arguments
 while [ $# -gt 0 ]; do
   case "$1" in
@@ -85,14 +90,6 @@ while [ $# -gt 0 ]; do
       build=0
       shift
       ;;
-    --library_tests)
-      library_tests=1
-      shift
-      ;;
-    --nolibrary_tests)
-      library_tests=0
-      shift
-      ;;
     --local)
       local=1
       shift
@@ -109,6 +106,14 @@ while [ $# -gt 0 ]; do
       system_tests=0
       shift
       ;;
+    --tests)
+      tests=1
+      shift
+      ;;
+    --notests)
+      tests=0
+      shift
+      ;;
     *)
       usage
       ;;
@@ -118,9 +123,12 @@ done
 # If no actions chosen, then tell the user
 if [ "${benchmark}" -eq 0 -a \
   "${build}" -eq 0 -a \
-  "${library_tests}" -eq 0 -a \
-  "${system_tests}" -eq 0 ]; then
-  fatal 'Error: No actions specified (for example, --build), exiting'
+  "${system_tests}" -eq 0 -a \
+  "${tests}" -eq 0 \
+]; then
+  echo 'No actions specified, defaulting to --build --tests'
+  build=1
+  tests=1
 fi
 
 # Running build local or remote?
@@ -155,7 +163,8 @@ for outfile in \
   tests/google-cloud-python-system/Dockerfile \
   tests/integration/Dockerfile \
   ; do
-  envsubst <"${outfile}".in >"${outfile}" '$DEBIAN_BASE_IMAGE $STAGING_IMAGE $GOOGLE_CLOUD_PROJECT_FOR_TESTS'
+  envsubst <"${outfile}".in >"${outfile}" \
+    '$DEBIAN_BASE_IMAGE $STAGING_IMAGE $GOOGLE_CLOUD_PROJECT_FOR_TESTS $TAG'
 done
 
 # Make some files available to the runtime builder Docker context
@@ -174,36 +183,27 @@ cp -a scripts/testdata/hello_world/main.py tests/eventlet/main.py
 # Build images and push to GCR
 if [ "${build}" -eq 1 ]; then
   echo "Building images"
-  ${gcloud_cmd} --config cloudbuild.yaml --substitutions "${substitutions}"
+  ${gcloud_cmd} --config cloudbuild.yaml --substitutions "${build_substitutions}"
 fi
 
-# Run just the library compatibility tests (for DPE Gardener bot usually)
-if [ "${library_tests}" -eq 1 ]; then
+# Run the tests that don't require (too many) external services
+if [ "${tests}" -eq 1 ]; then
   echo "Testing compatibility with popular Python libraries"
-  ${gcloud_cmd} --config cloudbuild_library_tests.yaml --substitutions "${substitutions}"
+  ${gcloud_cmd} --config cloudbuild_tests.yaml --substitutions "${substitutions}"
 fi
 
-# If both system tests and benchmarks are requested, run them both
-# even if one or the other has errors.  If the build step had errors,
-# this script will have already exited.
-exit_code=0
-
 # Run system tests
 if [ "${system_tests}" -eq 1 ]; then
   echo "Running system tests using project ${GOOGLE_CLOUD_PROJECT_FOR_TESTS}"
 
   trap "rm -f tests/google-cloud-python-system/credentials.json" EXIT
   cp "${GOOGLE_APPLICATION_CREDENTIALS_FOR_TESTS}" tests/google-cloud-python-system/credentials.json
-  ${gcloud_cmd} --config cloudbuild_system_tests.yaml --substitutions  "${substitutions}" || \
-    exit_code=1
+  ${gcloud_cmd} --config cloudbuild_system_tests.yaml --substitutions  "${substitutions}"
   rm -f tests/google-cloud-python-system/credentials.json
 fi
 
 # Run benchmarks
 if [ "${benchmark}" -eq 1 ] ; then
   echo "Running benchmark"
-  ${gcloud_cmd} --config cloudbuild_benchmark.yaml --substitutions  "${substitutions}" || \
-    exit_code=1
+  ${gcloud_cmd} --config cloudbuild_benchmark.yaml --substitutions  "${substitutions}"
 fi
-
-exit ${exit_code}
diff --git a/cloudbuild.yaml b/cloudbuild.yaml
index 68b5c5b..1eabb99 100644
--- a/cloudbuild.yaml
+++ b/cloudbuild.yaml
@@ -11,35 +11,12 @@ steps:
   name: gcr.io/cloud-builders/docker:latest
   args: ['build', '--tag=${_DOCKER_NAMESPACE}/python:${_TAG}',
          '--no-cache', '/workspace/runtime-image/']
-- # Validate structure of base runtime image
-  name: gcr.io/gcp-runtimes/structure_test:latest
-  args: [
-    '-i', '${_DOCKER_NAMESPACE}/python:${_TAG}',
-    '--config', '/workspace/tests/virtualenv/virtualenv_default.yaml',
-    '--config', '/workspace/tests/virtualenv/virtualenv_python34.yaml',
-    '--config', '/workspace/tests/virtualenv/virtualenv_python35.yaml',
-    '--config', '/workspace/tests/virtualenv/virtualenv_python36.yaml',
-    '--config', '/workspace/tests/no-virtualenv/no-virtualenv.yaml',
-    '--config', '/workspace/tests/python2-libraries/python2-libraries.yaml',
-    '--config', '/workspace/tests/python3-libraries/python3-libraries.yaml',
-    '--config', '/workspace/tests/license-test/license-test.yaml',
-    '-v'
-    ]
-- # Run compatibility tests
-  name: gcr.io/cloud-builders/docker:latest
-  args: ['build', '--tag=${_DOCKER_NAMESPACE}/python/tests/eventlet:${_TAG}',
-         '--no-cache', '/workspace/tests/eventlet/']
-- # Build image to run google client library unit tests
-  name: gcr.io/cloud-builders/docker:latest
-  args: ['build', '--tag=${_DOCKER_NAMESPACE}/python/tests/google-cloud-python:${_TAG}',
-         '--no-cache', '/workspace/tests/google-cloud-python/']
-- # Run google client library unit tests
-  name: ${_DOCKER_NAMESPACE}/python/tests/google-cloud-python:${_TAG}
 - # Build runtime builder image
   name: gcr.io/cloud-builders/docker:latest
   args: ['build', '--tag=${_BUILDER_DOCKER_NAMESPACE}/python/gen-dockerfile:${_TAG}',
          '--no-cache', '/workspace/builder/gen-dockerfile/']
 images: [
+  '${_DOCKER_NAMESPACE}/python/interpreter-builder:${_TAG}',
   '${_DOCKER_NAMESPACE}/python:${_TAG}',
   '${_BUILDER_DOCKER_NAMESPACE}/python/gen-dockerfile:${_TAG}',
 ]
diff --git a/cloudbuild_benchmark.yaml b/cloudbuild_benchmark.yaml
index 616991e..a960bc9 100644
--- a/cloudbuild_benchmark.yaml
+++ b/cloudbuild_benchmark.yaml
@@ -3,10 +3,6 @@ steps:
 - name: gcr.io/cloud-builders/docker:latest
   args: ['build', '--tag=${_DOCKER_NAMESPACE}/python/tests/benchmark:${_TAG}',
          '--no-cache', '/workspace/tests/benchmark/']
-  env: [
-    # Avoid warning about unused substitutions
-    'UNUSED1=${_BUILDER_DOCKER_NAMESPACE}',
-    ]
 images: [
   # Intentionally empty
 ]
diff --git a/cloudbuild_library_tests.yaml b/cloudbuild_library_tests.yaml
deleted file mode 100644
index f547d73..0000000
--- a/cloudbuild_library_tests.yaml
+++ /dev/null
@@ -1,20 +0,0 @@
-timeout: 1800s
-steps:
-- # Check that we can install important libraries without error
-  name: gcr.io/gcp-runtimes/structure_test:latest
-  args: [
-    '-i', '${_DOCKER_NAMESPACE}/python:${_TAG}',
-    '--config', '/workspace/tests/python2-libraries/python2-libraries.yaml',
-    '--config', '/workspace/tests/python3-libraries/python3-libraries.yaml',
-    '-v'
-    ]
-  env: [
-    # Avoid warning about unused substitutions
-    'UNUSED1=${_BUILDER_DOCKER_NAMESPACE}',
-    ]
-- # Run compatibility tests
-  name: gcr.io/cloud-builders/docker:latest
-  args: ['build', '--tag=${_DOCKER_NAMESPACE}/python/tests/eventlet:${_TAG}',
-         '--no-cache', '/workspace/tests/eventlet/']
-images: [
-]
diff --git a/cloudbuild_system_tests.yaml b/cloudbuild_system_tests.yaml
index f01a48e..3cac03e 100644
--- a/cloudbuild_system_tests.yaml
+++ b/cloudbuild_system_tests.yaml
@@ -4,10 +4,6 @@ steps:
   args: ['build', '--tag=${_DOCKER_NAMESPACE}/python/tests/google-cloud-python-system:${_TAG}',
          '--no-cache', '/workspace/tests/google-cloud-python-system/']
 - name: ${_DOCKER_NAMESPACE}/python/tests/google-cloud-python-system:${_TAG}
-  env: [
-    # Avoid warning about unused substitutions
-    'UNUSED1=${_BUILDER_DOCKER_NAMESPACE}',
-    ]
 images: [
   # Intentionally empty
 ]
diff --git a/cloudbuild_tests.yaml b/cloudbuild_tests.yaml
new file mode 100644
index 0000000..806e8b1
--- /dev/null
+++ b/cloudbuild_tests.yaml
@@ -0,0 +1,28 @@
+timeout: 3600s
+steps:
+- # Validate structure of base runtime image
+  name: gcr.io/gcp-runtimes/structure_test:latest
+  args: [
+    '-i', '${_DOCKER_NAMESPACE}/python:${_TAG}',
+    '--config', '/workspace/tests/virtualenv/virtualenv_default.yaml',
+    '--config', '/workspace/tests/virtualenv/virtualenv_python34.yaml',
+    '--config', '/workspace/tests/virtualenv/virtualenv_python35.yaml',
+    '--config', '/workspace/tests/virtualenv/virtualenv_python36.yaml',
+    '--config', '/workspace/tests/no-virtualenv/no-virtualenv.yaml',
+    '--config', '/workspace/tests/python2-libraries/python2-libraries.yaml',
+    '--config', '/workspace/tests/python3-libraries/python3-libraries.yaml',
+    '--config', '/workspace/tests/license-test/license-test.yaml',
+    '-v'
+    ]
+- # Run compatibility tests
+  name: gcr.io/cloud-builders/docker:latest
+  args: ['build', '--tag=${_DOCKER_NAMESPACE}/python/tests/eventlet:${_TAG}',
+         '--no-cache', '/workspace/tests/eventlet/']
+- # Build image to run google client library unit tests
+  name: gcr.io/cloud-builders/docker:latest
+  args: ['build', '--tag=${_DOCKER_NAMESPACE}/python/tests/google-cloud-python:${_TAG}',
+         '--no-cache', '/workspace/tests/google-cloud-python/']
+- # Run google client library unit tests
+  name: ${_DOCKER_NAMESPACE}/python/tests/google-cloud-python:${_TAG}
+images: [
+]