diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9d6ff580..cbec2f47 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,8 +18,8 @@ jobs:
     strategy:
       matrix:
         stack:
-          - scalingo-20
           - scalingo-22
+          - scalingo-24
     container:
       image: "scalingo/${{ matrix.stack }}:latest"
       env:
diff --git a/Makefile b/Makefile
index a55bf9a2..4e27bdaa 100644
--- a/Makefile
+++ b/Makefile
@@ -4,12 +4,12 @@ BASH_COMMAND := /bin/bash
 .DEFAULT := all
 
 all: test
-test: test20 test22
+test: test22 test24
 
-test20: STACK := "scalingo-20"
+test24: STACK := "scalingo-24"
 
-test20 test22: BASH_COMMAND := test/run
-test20 test22: IMAGE := "scalingo/$(STACK):latest"
-test20 test22:
+test22 test24: BASH_COMMAND := test/run
+test22 test24: IMAGE := "scalingo/$(STACK):latest"
+test22 test24:
 	@echo "Running tests in Docker using $(IMAGE)"
 	@docker run --pull always --mount type=bind,src=$(PWD),dst=/buildpack,readonly --workdir /buildpack --rm --interactive --tty --env "GITLAB_TOKEN=$(GITLAB_TOKEN)" --env "GITHUB_TOKEN=$(GITHUB_TOKEN)" --env "STACK=$(STACK)" $(IMAGE) bash -c "$(BASH_COMMAND)"
diff --git a/README.md b/README.md
index 778f6ca4..f110117c 100644
--- a/README.md
+++ b/README.md
@@ -486,4 +486,19 @@ Node.js script at that time.
 
 ## Contributing
 
-Please see the [CONTRIBUTING](/CONTRIBUTING.md) file for all the details.
+### Unit Tests
+
+The buildpack is tested with unit tests. One can execute them using `make`:
+
+```sh
+make
+```
+
+Understanding the root cause of a failing test is (not yet) easy. In case of failing test, we suggest you execute this single test by commenting all the other tests in `test/tests`. Then find the location of your test and add the following right after the failed test:
+
+```sh
+cat "${STD_OUT}"
+cat "${STD_ERR}"
+```
+
+Execute the test again, these two `cat` calls will output the stdout and stderr.
diff --git a/bin/compile b/bin/compile
index ba3496bc..bb8c54f0 100755
--- a/bin/compile
+++ b/bin/compile
@@ -22,7 +22,7 @@ if [ "$PHP_BUILDPACK_NO_NODE" != "true" ] ; then
 fi
 
 if [ -n "$BUILDPACK_DEBUG" ]; then
-    set -x
+  set -x
 fi
 
 BUILD_DIR="$1"
diff --git a/test/defaults b/test/defaults
index aafb43ab..2082c5a7 100644
--- a/test/defaults
+++ b/test/defaults
@@ -5,18 +5,18 @@ declare -gA default_nginx
 declare -gA default_composer
 declare -gA latest_composer
 
-# Defaults for scalingo-20:
-default_php["scalingo-20"]="8.1."
-default_nginx["scalingo-20"]="1.26."
-default_composer["scalingo-20"]="2.8."
-latest_composer["scalingo-20"]="2.8.8"
-
 # Defaults for scalingo-22:
-default_php["scalingo-22"]="8.1."
+default_php["scalingo-22"]="8.1." # This one depends on the semver stable rule configuration
 default_nginx["scalingo-22"]="1.28."
 default_composer["scalingo-22"]="2.8."
 latest_composer["scalingo-22"]="2.8.11"
 
+# Defaults for scalingo-24:
+default_php["scalingo-24"]="8.4."
+default_nginx["scalingo-24"]="1.28."
+default_composer["scalingo-24"]="2.8."
+latest_composer["scalingo-24"]="2.8.11"
+
 
 test::defaults::classic() {
 #
diff --git a/test/fixtures/nginx-1.28.0/composer/composer.json b/test/fixtures/nginx-1.28.0/composer/composer.json
new file mode 100644
index 00000000..ed11ecc4
--- /dev/null
+++ b/test/fixtures/nginx-1.28.0/composer/composer.json
@@ -0,0 +1,9 @@
+{
+    "extra": {
+        "paas": {
+            "engines": {
+                "nginx": "1.28.0"
+            }
+        }
+    }
+}
diff --git a/test/fixtures/nginx-1.28.0/composer/composer.lock b/test/fixtures/nginx-1.28.0/composer/composer.lock
new file mode 100644
index 00000000..4f967fe3
--- /dev/null
+++ b/test/fixtures/nginx-1.28.0/composer/composer.lock
@@ -0,0 +1,18 @@
+{
+    "_readme": [
+        "This file locks the dependencies of your project to a known state",
+        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
+        "This file is @generated automatically"
+    ],
+    "content-hash": "df7fd9ca7fdce9bf5ca88bbdb6baeb5f",
+    "packages": [],
+    "packages-dev": [],
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": [],
+    "prefer-stable": false,
+    "prefer-lowest": false,
+    "platform": [],
+    "platform-dev": [],
+    "plugin-api-version": "2.2.0"
+}
diff --git a/test/fixtures/nginx-1.29.0/composer/composer.json b/test/fixtures/nginx-1.29.0/composer/composer.json
new file mode 100644
index 00000000..7e1270d1
--- /dev/null
+++ b/test/fixtures/nginx-1.29.0/composer/composer.json
@@ -0,0 +1,9 @@
+{
+    "extra": {
+        "paas": {
+            "engines": {
+                "nginx": "1.29.0"
+            }
+        }
+    }
+}
diff --git a/test/fixtures/nginx-1.29.0/composer/composer.lock b/test/fixtures/nginx-1.29.0/composer/composer.lock
new file mode 100644
index 00000000..4f967fe3
--- /dev/null
+++ b/test/fixtures/nginx-1.29.0/composer/composer.lock
@@ -0,0 +1,18 @@
+{
+    "_readme": [
+        "This file locks the dependencies of your project to a known state",
+        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
+        "This file is @generated automatically"
+    ],
+    "content-hash": "df7fd9ca7fdce9bf5ca88bbdb6baeb5f",
+    "packages": [],
+    "packages-dev": [],
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": [],
+    "prefer-stable": false,
+    "prefer-lowest": false,
+    "platform": [],
+    "platform-dev": [],
+    "plugin-api-version": "2.2.0"
+}
diff --git a/test/nginx b/test/nginx
index 4d1f4e31..63009315 100644
--- a/test/nginx
+++ b/test/nginx
@@ -12,14 +12,14 @@ test::nginx::classic() {
 # the one expected.
 #
 
-    NGINX_VERSION="1.22.1"
+    NGINX_VERSION="1.28.0"
     export NGINX_VERSION
 
     test::utils::setupFixture "defaults/classic"
     test::utils::compile
     test::helpers::enter_prod
 
-    test::helpers::nginx "1.22.1"
+    test::helpers::nginx "1.28.0"
 }
 
 test::nginx::composer() {
@@ -28,11 +28,11 @@ test::nginx::composer() {
 # Specifying the nginx version only via composer.json
 #
 
-    test::utils::setupFixture "nginx-1.21.6/composer"
+    test::utils::setupFixture "nginx-1.28.0/composer"
     test::utils::compile
     test::helpers::enter_prod
 
-    test::helpers::nginx "1.21.6"
+    test::helpers::nginx "1.28.0"
 }
 
 #test::composer::nginx_version_via_env() {
@@ -59,30 +59,30 @@ test::nginx::composer_over_lower_classic() {
 # specified in NGINX_VERSION.
 #
 
-    NGINX_VERSION="1.21.6"
+    NGINX_VERSION="1.28.0"
     export NGINX_VERSION
 
-    test::utils::setupFixture "nginx-1.22.1/composer"
+    test::utils::setupFixture "nginx-1.29.0/composer"
     test::utils::compile
     test::helpers::enter_prod
 
-    test::helpers::nginx "1.22.1"
+    test::helpers::nginx "1.29.0"
 }
 
 test::nginx::composer_over_higher_classic() {
 #
 # Test a deployment of a PHP app using Composer
-# Specifying the Nginx version via  both composer.json and NGINX_VERSION.
+# Specifying the Nginx version via both composer.json and NGINX_VERSION.
 # And where the version specified in composer.json is lower than the one
 # specified in NGINX_VERSION.
 #
 
-    NGINX_VERSION="1.22.1"
+    NGINX_VERSION="1.29.0"
     export NGINX_VERSION
 
-    test::utils::setupFixture "nginx-1.21.6/composer"
+    test::utils::setupFixture "nginx-1.28.0/composer"
     test::utils::compile
     test::helpers::enter_prod
 
-    test::helpers::nginx "1.21.6"
+    test::helpers::nginx "1.28.0"
 }
diff --git a/test/utils b/test/utils
index 3f5cf448..62a2260d 100644
--- a/test/utils
+++ b/test/utils
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 # taken from
 # https://github.com/ryanbrainard/heroku-buildpack-testrunner/blob/master/lib/test_utils.sh
@@ -112,7 +112,7 @@ test::utils::assertMatches() {
 
 	local needle
 	local haystack
-	
+
 	needle="${1}"
 	haystack="${2}"