diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index ff424a04..b478feab 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -7,73 +7,19 @@ on:
   pull_request:
 
 jobs:
-  build:
-    name: 'PHP ${{ matrix.php.branch }}'
+  prepare-ci:
+    name: 'Prepare actions'
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        php:
-          - branch: '8.2'
-          - branch: '8.1'
-          - branch: '8.0'
-          - branch: '7.4'
-          - branch: '7.3'
-          - branch: '7.2'
-          - branch: '7.1'
-          - branch: '7.0'
-          - branch: '5.6'
-      # We want to fix failures individually.
-      fail-fast: false
     steps:
       - uses: actions/checkout@v3
 
       - name: Install Nix
         uses: cachix/install-nix-action@v18
 
-      - name: Set up Nix cache
-        uses: cachix/cachix-action@v12
-        with:
-          name: fossar
-          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-
-      - name: Set job parameters
-        id: params
-        run: |
-          branch=${{ matrix.php.branch }}
-          major=${branch%%.*}
-          minor=${branch#*.}
-          attr=php$major$minor
-          echo "major=$major" >> $GITHUB_OUTPUT
-          echo "attr=$attr" >> $GITHUB_OUTPUT
-
-      - name: Build PHP
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-php
-
-      - name: Build Imagick extension
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-imagick
-
-      - name: Build Redis extension
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-redis
-
-      - name: Build Redis 3 extension
-        if: ${{ steps.params.outputs.major < 8 }}
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-redis3
-
-      - name: Build MySQL extension
-        if: ${{ steps.params.outputs.major < 7 }}
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-mysql
-
-      - name: Build Xdebug extension
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-xdebug
-
-      - name: Build Tidy extension
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-tidy
-
-      - name: Check that composer PHAR works
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-composer-phar
-
-      - name: Validate php.extensions.mysqli default unix socket path
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-mysqli-socket-path
-
-      - name: Validate php.extensions.pdo_mysql default unix socket path
-        run: nix-build -A outputs.checks.x86_64-linux.${{ steps.params.outputs.attr }}-pdo_mysql-socket-path
+      - name: Generate actions
+        run: nix-shell .github/workflows/workflow-from-flake-checks.nix
+  test:
+    needs:
+      - prepare-ci
+    uses: ./.github/workflows/test.yaml
+    secrets: inherit
diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
new file mode 100644
index 00000000..6d4d123a
--- /dev/null
+++ b/.github/workflows/test.yaml
@@ -0,0 +1,134 @@
+{
+  "jobs": {
+    "test": {
+      "name": "PHP ${{ matrix.php.branch }}",
+      "runs-on": "${{ matrix.os.image }}",
+      "steps": [
+        {
+          "uses": "actions/checkout@v3"
+        },
+        {
+          "name": "Install Nix",
+          "uses": "cachix/install-nix-action@v18"
+        },
+        {
+          "name": "Set up Nix cache",
+          "uses": "cachix/cachix-action@v10",
+          "with": {
+            "authToken": "${{ secrets.CACHIX_AUTH_TOKEN }}",
+            "name": "fossar"
+          }
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\",\"php80\",\"php81\",\"php82\"]'), matrix.php.attr) }}",
+          "name": "Check that composer PHAR works",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-composer-phar"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\",\"php80\",\"php81\",\"php82\"]'), matrix.php.attr) }}",
+          "name": "Build Imagick extension",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-imagick"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\"]'), matrix.php.attr) }}",
+          "name": "Build MySQL extension",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-mysql"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\",\"php80\",\"php81\",\"php82\"]'), matrix.php.attr) }}",
+          "name": "Validate php.extensions.mysqli default unix socket path",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-mysqli-socket-path"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\",\"php80\",\"php81\",\"php82\"]'), matrix.php.attr) }}",
+          "name": "Validate php.extensions.pdo_mysql default unix socket path",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-pdo_mysql-socket-path"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\",\"php80\",\"php81\",\"php82\"]'), matrix.php.attr) }}",
+          "name": "Build PHP",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-php"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\",\"php80\",\"php81\",\"php82\"]'), matrix.php.attr) }}",
+          "name": "Build Redis extension",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-redis"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\"]'), matrix.php.attr) }}",
+          "name": "Build Redis 3 extension",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-redis3"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\",\"php80\",\"php81\",\"php82\"]'), matrix.php.attr) }}",
+          "name": "Build Tidy extension",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-tidy"
+        },
+        {
+          "if": "${{ contains(fromJSON('[\"aarch64-darwin\",\"aarch64-linux\",\"x86_64-darwin\",\"x86_64-linux\"]'), matrix.os.platform) && contains(fromJSON('[\"php56\",\"php70\",\"php71\",\"php72\",\"php73\",\"php74\",\"php80\",\"php81\",\"php82\"]'), matrix.php.attr) }}",
+          "name": "Build Xdebug extension",
+          "run": "nix-build -A outputs.checks.${{ matrix.os.platform }}.${{ matrix.php.attr }}-xdebug"
+        }
+      ],
+      "strategy": {
+        "fail-fast": false,
+        "matrix": {
+          "os": [
+            {
+              "image": "ubuntu-latest",
+              "platform": "x86_64-linux"
+            }
+          ],
+          "php": [
+            {
+              "attr": "php56",
+              "branch": "5.6"
+            },
+            {
+              "attr": "php70",
+              "branch": "7.0"
+            },
+            {
+              "attr": "php71",
+              "branch": "7.1"
+            },
+            {
+              "attr": "php72",
+              "branch": "7.2"
+            },
+            {
+              "attr": "php73",
+              "branch": "7.3"
+            },
+            {
+              "attr": "php74",
+              "branch": "7.4"
+            },
+            {
+              "attr": "php80",
+              "branch": "8.0"
+            },
+            {
+              "attr": "php81",
+              "branch": "8.1"
+            },
+            {
+              "attr": "php82",
+              "branch": "8.2"
+            }
+          ]
+        }
+      }
+    }
+  },
+  "name": "Test",
+  "on": {
+    "workflow_call": {
+      "secrets": {
+        "CACHIX_AUTH_TOKEN": {
+          "required": true
+        }
+      }
+    }
+  }
+}
diff --git a/.github/workflows/workflow-from-flake-checks.nix b/.github/workflows/workflow-from-flake-checks.nix
new file mode 100644
index 00000000..3a570d34
--- /dev/null
+++ b/.github/workflows/workflow-from-flake-checks.nix
@@ -0,0 +1,151 @@
+# Runs Nix flake checks individually with group markers for GitHub Actions.
+# Invoke with `nix-shell workflow-from-flake-checks.nix`
+
+let
+  self = import ../..;
+
+  pkgs = self.inputs.nixpkgs.legacyPackages.${builtins.currentSystem};
+  inherit (self.inputs.nixpkgs) lib;
+
+  checkAttrs =
+    lib.foldl'
+      (
+        acc:
+        {
+          name,
+          value,
+        }:
+
+        acc // {
+          "${name}" = {
+            inherit (value) description;
+            platforms = acc.${name}.platforms or {} // { "${value.platform}" = null; };
+            phps = acc.${name}.phps or {} // { "${value.php}" = null; };
+          };
+        }
+      )
+      {}
+      (
+        builtins.concatLists (
+          lib.mapAttrsToList
+            (
+              platform:
+              checks:
+
+              lib.mapAttrsToList
+                (
+                  attr:
+                  check:
+
+                  let
+                    match = builtins.match "(php[0-9]+)-(.+)" attr;
+                  in
+                  {
+                    name = builtins.head (builtins.tail match);
+                    value = {
+                      inherit (check) description;
+                      inherit platform;
+                      php = builtins.head match;
+                    };
+                  }
+                )
+                checks
+            )
+            self.outputs.checks
+        )
+      );
+
+  packages = self.outputs.packages.${builtins.currentSystem};
+  phpPackages = builtins.filter (name: builtins.match "php[0-9]+" name != null) (builtins.attrNames packages);
+
+  workflow = {
+    name = "Test";
+
+    on = {
+      workflow_call = {
+        secrets = {
+          CACHIX_AUTH_TOKEN = {
+            required = true;
+          };
+        };
+      };
+    };
+
+    jobs = {
+      test = {
+        name = "PHP \${{ matrix.php.branch }}";
+        runs-on = "\${{ matrix.os.image }}";
+        steps = [
+          {
+            uses = "actions/checkout@v3";
+          }
+          {
+            name = "Install Nix";
+            uses = "cachix/install-nix-action@v18";
+          }
+          {
+            name = "Set up Nix cache";
+            uses = "cachix/cachix-action@v10";
+            "with" = {
+              authToken = "\${{ secrets.CACHIX_AUTH_TOKEN }}";
+              name = "fossar";
+            };
+          }
+        ]
+        ++ lib.mapAttrsToList
+          (
+            attr:
+            check:
+
+            {
+              name = check.description;
+              "if" = "\${{ contains(fromJSON('${lib.escape [ "\\" "'" ] (builtins.toJSON (builtins.attrNames check.platforms))}'), matrix.os.platform) && contains(fromJSON('${lib.escape [ "\\" "'" ] (builtins.toJSON (builtins.attrNames check.phps))}'), matrix.php.attr) }}";
+              run = "nix-build -A outputs.checks.\${{ matrix.os.platform }}.\${{ matrix.php.attr }}-${attr}";
+            }
+          )
+          checkAttrs
+        ;
+        strategy = {
+          # We want to fix failures individually.
+          fail-fast = false;
+          matrix = {
+            os = [
+              {
+                image = "ubuntu-latest";
+                platform = "x86_64-linux";
+              }
+            ];
+            php =
+              builtins.map
+                (
+                  phpAttr:
+
+                  {
+                    branch = lib.versions.majorMinor packages.${phpAttr}.version;
+                    attr = phpAttr;
+                  }
+                )
+                phpPackages;
+          };
+        };
+      };
+    };
+  };
+in
+
+pkgs.stdenv.mkDerivation {
+  name = "workflow-from-flake-checks";
+
+  buildCommand = ''
+    echo 'Please run `nix-shell .github/workflows/workflow-from-flake-checks.nix`, `nix-build` cannot be used.' > /dev/stderr
+    exit 1
+  '';
+
+  shellHook =
+    ''
+      set -o errexit
+      echo ${lib.escapeShellArgs [ (builtins.toJSON workflow) ]} | ${pkgs.jq}/bin/jq . > .github/workflows/test.yaml
+      exit 0
+    ''
+    ;
+}
diff --git a/checks.nix b/checks.nix
index b322f85d..842719f0 100644
--- a/checks.nix
+++ b/checks.nix
@@ -1,160 +1,96 @@
 {
-  system,
-  packages,
-  pkgs,
+  lib,
+  php,
+  runCommand,
 }:
 
-let
-  phpPackages = builtins.filter (name: builtins.match "php[0-9]+" name != null) (builtins.attrNames packages);
-
-  checks = {
-    php = {
-      description = "Build PHP";
-      drv = { php, ... }: php;
-    };
-
-    imagick = {
-      description = "Build Imagick extension";
-      drv = { php, ... }: php.extensions.imagick;
-    };
-
-    redis = {
-      description = "Build Redis extension";
-      drv = { php, ... }: php.extensions.redis;
-    };
-
-    redis3 = {
-      description = "Build Redis 3 extension";
-      enabled = { php, lib, ... }: lib.versionOlder php.version "8";
-      drv = { php, ... }: php.extensions.redis3;
-    };
-
-    mysql = {
-      description = "Build MySQL extension";
-      enabled = { php, lib, ... }: lib.versionOlder php.version "7";
-      drv = { php, ... }: php.extensions.mysql;
-    };
-
-    xdebug = {
-      description = "Build Xdebug extension";
-      drv = { php, ... }: php.extensions.xdebug;
-    };
+{
+  php = {
+    description = "Build PHP";
+    drv = php;
+  };
 
-    tidy = {
-      description = "Build Tidy extension";
-      drv = { php, ... }: php.extensions.tidy;
-    };
+  imagick = {
+    description = "Build Imagick extension";
+    drv = php.extensions.imagick;
+  };
 
-    composer-phar = {
-      description = "Check that composer PHAR works";
-      drv =
-        { pkgs, php, ... }:
-        pkgs.runCommand
-          "composer-phar-check"
-          {
-            buildInputs = [
-              php.packages.composer
-            ];
-          }
-          ''
-            composer --version
-            touch "$out"
-          '';
-    };
+  redis = {
+    description = "Build Redis extension";
+    drv = php.extensions.redis;
+  };
 
-    mysqli-socket-path = {
-      description = "Validate php.extensions.mysqli default unix socket path";
-      drv =
-        { pkgs, php, ... }:
-        pkgs.runCommand
-          "mysqli-socket-path-check"
-          {
-            buildInputs = [
-              (php.withExtensions ({ all, ... }: [
-                all.mysqli
-              ]))
-            ];
-          }
-          ''
-            php -r "echo ini_get('mysqli.default_socket') . PHP_EOL;" | grep /run/mysqld/mysqld.sock
-            touch "$out"
-          '';
-    };
+  redis3 = {
+    description = "Build Redis 3 extension";
+    enabled = lib.versionOlder php.version "8";
+    drv = php.extensions.redis3;
+  };
 
-    pdo_mysql-socket-path = {
-      description = "Validate php.extensions.pdo_mysql default unix socket path";
-      drv =
-        { pkgs, php, ... }:
-        pkgs.runCommand
-          "pdo_mysql-socket-path-check"
-          {
-            buildInputs = [
-              (php.withExtensions ({ all, ... }: [
-                all.pdo_mysql
-              ]))
-            ];
-          }
-          ''
-            php -r "echo ini_get('pdo_mysql.default_socket') . PHP_EOL;" | grep /run/mysqld/mysqld.sock
-            touch "$out"
-          '';
-    };
+  mysql = {
+    description = "Build MySQL extension";
+    enabled = lib.versionOlder php.version "7";
+    drv = php.extensions.mysql;
   };
 
-  inherit (pkgs) lib;
+  xdebug = {
+    description = "Build Xdebug extension";
+    drv = php.extensions.xdebug;
+  };
 
-  /* AttrSet<phpName, AttrSet<checkName, checkDrv>> */
-  checksPerVersion =
-    lib.listToAttrs (
-      builtins.map
-        (phpName:
-          let
-            php = packages.${phpName};
-            phpVersion = lib.versions.majorMinor php.version;
-            args = { inherit lib php pkgs system; };
-            supportedChecks = lib.filterAttrs (_name: { enabled ? lib.const true, ... }: enabled args) checks;
-          in
-          {
-            name = phpName;
-            value =
-              lib.mapAttrs
-                (
-                  _name:
-                  {
-                    description,
-                    drv,
-                    ...
-                  }:
+  tidy = {
+    description = "Build Tidy extension";
+    drv = php.extensions.tidy;
+  };
 
-                  let
-                    check = drv args;
-                  in
-                  check // {
-                    passthru = check.passthru or { } // {
-                      description = "PHP ${phpVersion} – ${description}";
-                    };
-                  }
-                )
-                supportedChecks;
-          }
-        )
-        phpPackages
-    );
-in
-lib.foldAttrs
-  lib.mergeAttrs
-  {}
-  (
-    lib.mapAttrsToList
-    (
-      phpName:
+  composer-phar = {
+    description = "Check that composer PHAR works";
+    drv =
+      runCommand
+        "composer-phar-check"
+        {
+          buildInputs = [
+            php.packages.composer
+          ];
+        }
+        ''
+          composer --version
+          touch "$out"
+        '';
+  };
 
-      lib.mapAttrs'
-        (
-          name:
+  mysqli-socket-path = {
+    description = "Validate php.extensions.mysqli default unix socket path";
+    drv =
+      runCommand
+        "mysqli-socket-path-check"
+        {
+          buildInputs = [
+            (php.withExtensions ({ all, ... }: [
+              all.mysqli
+            ]))
+          ];
+        }
+        ''
+          php -r "echo ini_get('mysqli.default_socket') . PHP_EOL;" | grep /run/mysqld/mysqld.sock
+          touch "$out"
+        '';
+  };
 
-          lib.nameValuePair "${phpName}-${name}"
-        )
-    )
-    checksPerVersion
-  )
+  pdo_mysql-socket-path = {
+    description = "Validate php.extensions.pdo_mysql default unix socket path";
+    drv =
+      runCommand
+        "pdo_mysql-socket-path-check"
+        {
+          buildInputs = [
+            (php.withExtensions ({ all, ... }: [
+              all.pdo_mysql
+            ]))
+          ];
+        }
+        ''
+          php -r "echo ini_get('pdo_mysql.default_socket') . PHP_EOL;" | grep /run/mysqld/mysqld.sock
+          touch "$out"
+        '';
+  };
+}
diff --git a/flake.nix b/flake.nix
index a5ecb1a5..43f9f260 100644
--- a/flake.nix
+++ b/flake.nix
@@ -32,9 +32,67 @@
           inherit (pkgs) php php56 php70 php71 php72 php73 php74 php80 php81 php82;
         };
 
-        checks = import ./checks.nix {
-          inherit packages pkgs system;
-        };
+        checks =
+          let
+            phpPackages = builtins.filter (name: builtins.match "php[0-9]+" name != null) (builtins.attrNames packages);
+
+            inherit (pkgs) lib;
+
+
+            /* AttrSet<phpName, AttrSet<checkName, checkDrv>> */
+            checksPerVersion =
+              lib.listToAttrs (
+                builtins.map
+                  (phpName:
+                    let
+                      php = packages.${phpName};
+                      phpVersion = lib.versions.majorMinor php.version;
+                      checks = import ./checks.nix {
+                        inherit lib php;
+                        inherit (pkgs) runCommand;
+                      };
+                      supportedChecks = lib.filterAttrs (_name: { enabled ? true, ... }: enabled) checks;
+                    in
+                    {
+                      name = phpName;
+                      value =
+                        lib.mapAttrs
+                          (
+                            _name:
+                            {
+                              description,
+                              drv,
+                              ...
+                            }:
+
+                            drv // {
+                              inherit description;
+                              phpBranch = phpVersion;
+                            }
+                          )
+                          supportedChecks;
+                    }
+                  )
+                  phpPackages
+              );
+          in
+          lib.foldAttrs
+            lib.mergeAttrs
+            {}
+            (
+              lib.mapAttrsToList
+              (
+                phpName:
+
+                lib.mapAttrs'
+                  (
+                    name:
+
+                    lib.nameValuePair "${phpName}-${name}"
+                  )
+              )
+              checksPerVersion
+            );
       }
     ) // {
       overlays.default = import ./pkgs/phps.nix nixpkgs.outPath;