diff --git a/check-utils.nix b/check-utils.nix
new file mode 100644
index 0000000..809d3ed
--- /dev/null
+++ b/check-utils.nix
@@ -0,0 +1,22 @@
+systemOrPkgs:
+let
+  str = it: if it == null then "null" else (toString it);
+  system = systemOrPkgs.system or systemOrPkgs;
+  test = name: command: derivation {
+    inherit name system;
+    builder = "/bin/sh";
+    args = [ "-c" command ];
+  };
+in
+{
+
+  isEqual = a: b:
+    if a == b
+    then test "SUCCESS__${str a}__IS_EQUAL__${str b}" "echo success > $out"
+    else test "FAILURE__${str a}__NOT_EQUAL__${str b}" "exit 1";
+
+  hasKey = attrset: key:
+    if attrset ? ${str key}
+    then test "SUCCESS__${str key}__EXISTS_IN_ATTRSET" "echo success > $out"
+    else test "FAILURE__${str key}__DOES_NOT_EXISTS_IN_ATTRSET_SIZE_${str(builtins.length (builtins.attrNames attrset))}" "exit 1";
+}
diff --git a/default.nix b/default.nix
index f81a59c..f61aed2 100644
--- a/default.nix
+++ b/default.nix
@@ -135,14 +135,18 @@ let
   # This function tries to capture a common flake pattern.
   simpleFlake = import ./simpleFlake.nix { inherit lib; };
 
+  # Helper functions for Nix evaluation
+  check-utils = import ./check-utils.nix;
+
   lib = {
     inherit
       allSystems
+      check-utils
       defaultSystems
       eachDefaultSystem
       eachSystem
-      flattenTree
       filterPackages
+      flattenTree
       mkApp
       simpleFlake
       ;
diff --git a/examples/checks-utils/flake.nix b/examples/checks-utils/flake.nix
new file mode 100644
index 0000000..4b16e1c
--- /dev/null
+++ b/examples/checks-utils/flake.nix
@@ -0,0 +1,29 @@
+{
+  description = "Flake utils demo";
+
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        inherit (flake-utils.lib.check-utils system) isEqual hasKey;
+
+        testDataset = { key1 = "value1"; key2 = "value2"; key3 = "value3"; };
+      in
+      rec {
+        checks = {
+          valid_key1 = isEqual testDataset.key1 "value1";
+          contains_key2 = hasKey testDataset "key2";
+
+          failing_valid_key1 = isEqual testDataset.key1 "failing-data";
+          failing_contains_key2 = hasKey testDataset "failing-data";
+
+          number_formatting_isEqual = isEqual testDataset.key1 123;
+          number_formatting_hasKey = hasKey testDataset 123;
+
+          null_formatting_key1 = isEqual testDataset.key1 null;
+          null_formatting_hasKey = hasKey testDataset null;
+        };
+      }
+    );
+}
diff --git a/filterPackages.nix b/filterPackages.nix
index 6cd935d..5bd4eba 100644
--- a/filterPackages.nix
+++ b/filterPackages.nix
@@ -6,11 +6,12 @@ let
   nameValuePair = name: value: { inherit name value; };
   filterAttrs = pred: set:
     listToAttrs (
-      concatMap (name:
-        let v = set.${name}; in
-          if pred name v then [(nameValuePair name v)] else []
-      )
-      (attrNames set)
+      concatMap
+        (name:
+          let v = set.${name}; in
+          if pred name v then [ (nameValuePair name v) ] else [ ]
+        )
+        (attrNames set)
     );
 
   # Everything that nix flake check requires for the packages output
@@ -22,9 +23,9 @@ let
       isBroken = meta.broken or false;
       platforms = meta.hydraPlatforms or meta.platforms or allSystems;
     in
-      # check for isDerivation, so this is independently useful of
+    # check for isDerivation, so this is independently useful of
       # flattenTree, which also does filter on derviations
-      isDerivation v && !isBroken && builtins.elem system platforms
+    isDerivation v && !isBroken && builtins.elem system platforms
   ;
 in
 filterAttrs sieve packages