diff --git a/.github/workflows/drupal-contrib-integration-test.yml b/.github/workflows/drupal-contrib-integration-test.yml
index b28ac3d..052a977 100644
--- a/.github/workflows/drupal-contrib-integration-test.yml
+++ b/.github/workflows/drupal-contrib-integration-test.yml
@@ -175,6 +175,18 @@ jobs:
           echo "--- end ---"
           echo "$MODULES" | grep -iw "${{ matrix.project }}"
 
+      - name: Verify workspace — PHPUnit functional test runs
+        # Runs a core test (present in every project's web root) rather than
+        # a module-specific one, so this step doesn't need to vary per matrix
+        # entry. Same regression class as drupal-core issue #211: if this
+        # template ever stopped setting SIMPLETEST_BASE_URL to a value
+        # reachable from inside the web container, every functional test
+        # would fail with "You must provide a SIMPLETEST_BASE_URL
+        # environment variable".
+        run: |
+          coder ssh ${{ env.WORKSPACE_NAME }} -- env -C /home/coder/${{ matrix.project }} \
+            ddev phpunit --filter testTitle web/core/modules/system/tests/src/Functional/System/PageTitleTest.php
+
       - name: Record expected host directory
         run: |
           OWNER=$(coder whoami --output json | jq -r 'if type == "array" then .[0].username else .username end')
@@ -562,6 +574,18 @@ jobs:
           echo "--- end ---"
           echo "$MODULES" | grep -iw "${{ matrix.project }}"
 
+      - name: Verify workspace — PHPUnit functional test runs
+        # Runs a core test (present in every project's web root) rather than
+        # a module-specific one, so this step doesn't need to vary per matrix
+        # entry. Same regression class as drupal-core issue #211: if this
+        # template ever stopped setting SIMPLETEST_BASE_URL to a value
+        # reachable from inside the web container, every functional test
+        # would fail with "You must provide a SIMPLETEST_BASE_URL
+        # environment variable".
+        run: |
+          coder ssh ${{ env.WORKSPACE_NAME }} -- env -C /home/coder/${{ matrix.project }} \
+            ddev phpunit --filter testTitle web/core/modules/system/tests/src/Functional/System/PageTitleTest.php
+
       - name: Record owner
         run: |
           OWNER=$(coder whoami --output json | jq -r 'if type == "array" then .[0].username else .username end')
diff --git a/.github/workflows/drupal-integration-test.yml b/.github/workflows/drupal-integration-test.yml
index e2dc8f2..6aad51f 100644
--- a/.github/workflows/drupal-integration-test.yml
+++ b/.github/workflows/drupal-integration-test.yml
@@ -159,6 +159,17 @@ jobs:
         name: Verify workspace — Drush DB connected
         run: coder ssh ${{ env.WORKSPACE_NAME }} -- ddev drush status --fields=db-status | grep -i connected
 
+      - &verify-phpunit
+        # Regression check for #211: amateescu/ddev-drupal-dev's own
+        # SIMPLETEST_BASE_URL=${DDEV_PRIMARY_URL} is empty because this
+        # template always omits ddev-router, which broke every phpunit
+        # functional test. See the SIMPLETEST_BASE_URL override written in
+        # template.tf's Step 4.
+        name: Verify workspace — PHPUnit functional test runs (#211)
+        run: |
+          coder ssh ${{ env.WORKSPACE_NAME }} -- \
+            ddev phpunit --filter testTitle core/modules/system/tests/src/Functional/System/PageTitleTest.php
+
       - &record-host-dir
         name: Record expected host directory
         run: |
@@ -309,6 +320,7 @@ jobs:
       - *verify-ddev
       - *verify-webroot
       - *verify-drush
+      - *verify-phpunit
       - *record-host-dir
       - *verify-http
 
diff --git a/drupal-contrib/template.tf b/drupal-contrib/template.tf
index d471f93..c796d31 100644
--- a/drupal-contrib/template.tf
+++ b/drupal-contrib/template.tf
@@ -687,6 +687,17 @@ COMPOSE_EOF
       # HEAD as the workflow comment above claims.
       DRUPAL_CORE_CONSTRAINT="^$DRUPAL_VERSION"
       if [ "$DRUPAL_VERSION" = "12" ]; then
+        # "12.x-dev" isn't a literal branch name -- it's the version string that
+        # drupal/core's composer.json branch-alias (extra.branch-alias) maps its
+        # actual default git branch onto, so this constraint resolves to the
+        # HEAD of that branch (currently "main"; installed packages report as
+        # "dev-main"). People fixing D12 issues normally work against "main"
+        # directly, so this constraint is meant to track exactly that -- it's
+        # just expressed as a version, not a branch name, because that's what
+        # lets other packages' "^12"-style requirements resolve against the
+        # same install (the reason #212 picked this form over "dev-main"
+        # literally). Expect this whole workaround to go away once 12.0.0
+        # ships and a normal tagged release exists to depend on instead.
         DRUPAL_CORE_CONSTRAINT="12.x-dev"
       fi
       ddev dotenv set .ddev/.env.web --drupal-core "$DRUPAL_CORE_CONSTRAINT"
@@ -738,6 +749,22 @@ COMPOSE_EOF
         # symfony/runtime) that aren't pre-listed in allow-plugins.
         jq 'if .config == null then .config = {} else . end | .config["allow-plugins"] = true' composer.json > composer.json.tmp && mv composer.json.tmp composer.json
 
+        # D12 has no stable tagged release yet, so DRUPAL_CORE_CONSTRAINT below
+        # resolves to the 12.x-dev branch. Composer's default dist install for a
+        # -dev/branch version fetches a GitHub zipball (a git-archive snapshot),
+        # which honors drupal/core's own .gitattributes export-ignore rules and
+        # strips the core/tests directory -- so any test referencing core (e.g.
+        # `ddev phpunit web/core/modules/...`) fails with "Cannot open bootstrap
+        # script core/tests/bootstrap.php". A real `git clone` (source install)
+        # does not apply export-ignore, so force source installs for drupal/core
+        # on D12 only -- D10/D11 use real tagged releases, whose dist packages
+        # already include tests, and forcing source there would just slow down
+        # every install for no benefit.
+        if [ "$DRUPAL_VERSION" = "12" ]; then
+          jq 'if .config == null then .config = {} else . end | .config["preferred-install"]["drupal/core"] = "source"' composer.json > composer.json.tmp && mv composer.json.tmp composer.json
+          log_setup "✓ drupal/core preferred-install set to source (D12 dev branch strips core/tests from dist)"
+        fi
+
         # Obtain a GitHub token for Composer OAuth — routes downloads through the
         # authenticated GitHub API instead of anonymous codeload.github.com
         # (which is prone to transient HTTP/2 400s and rate limits).
diff --git a/drupal-core/template.tf b/drupal-core/template.tf
index 468d51a..7692a7f 100644
--- a/drupal-core/template.tf
+++ b/drupal-core/template.tf
@@ -393,6 +393,8 @@ resource "coder_agent" "main" {
     elif [ -f "$HOME/.gitignore_global" ]; then
       grep -qxF 'config.coder.yaml' "$HOME/.gitignore_global" || \
         echo 'config.coder.yaml' >> "$HOME/.gitignore_global"
+      grep -qxF 'config.zzz-coder-test-env.yaml' "$HOME/.gitignore_global" || \
+        echo 'config.zzz-coder-test-env.yaml' >> "$HOME/.gitignore_global"
     fi
     if [ -n "$CODER_WORKSPACE_OWNER_NAME" ]; then
       git config --global user.name "$CODER_WORKSPACE_OWNER_NAME"
@@ -809,6 +811,37 @@ WELCOME_STATIC
       fi
 
       if [ "$SETUP_FAILED" != "true" ]; then
+        # The add-on's own .ddev/config.drupal-dev.yaml sets SIMPLETEST_BASE_URL
+        # from DDEV_PRIMARY_URL, but this template always omits ddev-router (see
+        # Step 2), and DDEV leaves DDEV_PRIMARY_URL empty whenever the router is
+        # disabled -- so phpunit fails every functional test with "You must
+        # provide a SIMPLETEST_BASE_URL environment variable" (fixes #211).
+        # Override it with the web container's own Docker-network hostname,
+        # which is always reachable from both PHP-CLI and the chrome container
+        # regardless of routing. The filename must sort alphabetically after
+        # "config.drupal-dev.yaml" so DDEV layers it on top and this value wins.
+        #
+        # BROWSERTEST_OUTPUT_BASE_URL only prefixes the human-clickable debug
+        # links phpunit prints for failed browser tests -- those HTML
+        # snapshots live in the docroot and are served over the same URL as
+        # the site itself, so point it at the real Coder proxy URL (matches
+        # coder_app.drupal-site's subdomain) rather than the container-only
+        # http://web, so the links are actually openable from outside.
+        if [ -n "$CODER_DOMAIN" ]; then
+          BROWSERTEST_URL="https://drupal-site--$${CODER_WORKSPACE_NAME}--$${CODER_WORKSPACE_OWNER_NAME}.$CODER_DOMAIN"
+        else
+          BROWSERTEST_URL="http://web"
+        fi
+        cat > .ddev/config.zzz-coder-test-env.yaml << TESTENV_EOF
+#ddev-generated
+#ddev-silent-no-warn
+# Auto-generated by workspace startup -- do not edit. See Step 4 in template.tf.
+web_environment:
+  - SIMPLETEST_BASE_URL=http://web
+  - BROWSERTEST_OUTPUT_BASE_URL=$BROWSERTEST_URL
+TESTENV_EOF
+        log_setup "✓ .ddev/config.zzz-coder-test-env.yaml written (SIMPLETEST_BASE_URL override)"
+
         log_setup "Restarting DDEV to activate add-on..."
         ddev restart >> "$SETUP_LOG" 2>&1 || true
 
diff --git a/image/scripts/.gitignore_global b/image/scripts/.gitignore_global
index 261c962..1930893 100644
--- a/image/scripts/.gitignore_global
+++ b/image/scripts/.gitignore_global
@@ -1,5 +1,6 @@
 # DDEV Coder integration
 config.coder.yaml
+config.zzz-coder-test-env.yaml
 
 # macOS
 .DS_Store