diff --git a/Dockerfile.lsphp b/Dockerfile.lsphp
index 16420d6..9171365 100644
--- a/Dockerfile.lsphp
+++ b/Dockerfile.lsphp
@@ -76,6 +76,20 @@ RUN set -e; \
     printf '%s' "$RTV" > /build-out/lsphp.version; \
     echo "cac_path_parity will be compiled against lsphp${PHPVER} $RTV"
 
+## Build, then RUN THE .phpt SUITE as a build gate. Before this, ext/…/tests/
+## existed but nothing ever executed it — neither this Dockerfile nor
+## .gitea/workflows/build-push.yaml — so six green tests were documentation. It
+## costs ~1s per PHP version and it runs against the SAME lsphp build the .so
+## will ship next to.
+##
+## Two guards around `make test`, because its default failure mode is silence:
+##  - if PHP_EXECUTABLE is missing the Makefile prints "Cannot run tests without
+##    CLI sapi." and EXITS 0. The lsphp packages do ship a real CLI
+##    (php-config --php-binary => .../bin/phpN.N), but assert it rather than
+##    trusting it.
+##  - a run that executes ZERO tests also exits 0, so assert the summary shows
+##    every .phpt in the directory both ran and passed. Same reasoning as the
+##    `lsphp -i` probe below: an assertion that cannot fail is worse than none.
 COPY ./ext/cac-path-parity /usr/src/cac-path-parity
 RUN set -e; \
     cd /usr/src/cac-path-parity; \
@@ -83,6 +97,29 @@ RUN set -e; \
     ./configure --enable-cac-path-parity \
         --with-php-config=/usr/local/lsws/lsphp${PHPVER}/bin/php-config; \
     make -j"$(nproc)"; \
+    PHP_BIN=$(/usr/local/lsws/lsphp${PHPVER}/bin/php-config --php-binary); \
+    if [ ! -x "$PHP_BIN" ]; then \
+        echo "FATAL: no CLI php at '$PHP_BIN' — \`make test\` would print" >&2; \
+        echo "       'Cannot run tests without CLI sapi.' and exit 0." >&2; \
+        exit 1; \
+    fi; \
+    EXPECTED=$(ls tests/*.phpt | wc -l); \
+    if [ "$EXPECTED" -lt 1 ]; then echo "FATAL: no .phpt tests found" >&2; exit 1; fi; \
+    if ! NO_INTERACTION=1 REPORT_EXIT_STATUS=1 make test >/tmp/make-test.log 2>&1; then \
+        cat /tmp/make-test.log >&2; \
+        echo "FATAL: cac_path_parity .phpt suite FAILED — not shipping this .so." >&2; \
+        exit 1; \
+    fi; \
+    cat /tmp/make-test.log; \
+    if ! grep -Eq "^Number of tests : +${EXPECTED} +${EXPECTED} *$" /tmp/make-test.log; then \
+        echo "FATAL: expected all ${EXPECTED} .phpt tests to run; the summary above disagrees." >&2; \
+        exit 1; \
+    fi; \
+    if ! grep -Eq "^Tests failed +: +0 " /tmp/make-test.log; then \
+        echo "FATAL: run-tests.php reported failures." >&2; \
+        exit 1; \
+    fi; \
+    echo "cac_path_parity: ${EXPECTED}/${EXPECTED} .phpt tests passed"; \
     cp modules/cac_path_parity.so /build-out/
 
 ## ---- stage 2: the shipped sidecar image ------------------------------------