[Backport release-25.05] lib/tests/test-with-nix: run misc.nix and fetchers.nix tests in the derivation (#434761)

lib/tests/check-eval.nix

@@ -1,10 +0,0 @@
-# Throws an error if any of our lib tests fail.
-
-let
-  tests = [
-    "misc"
-    "systems"
-  ];
-  all = builtins.concatLists (map (f: import (./. + "/${f}.nix")) tests);
-in
-if all == [ ] then null else throw (builtins.toJSON all)

lib/tests/misc.nix

@@ -145,6 +145,11 @@ let
       inherit expected;
     };
 
+  dummyDerivation = derivation {
+    name = "name";
+    builder = "builder";
+    system = "system";
+  };
 in
 
 runTests {
@@ -782,18 +787,8 @@ runTests {
   };
 
   testSplitStringsDerivation = {
-    expr = take 3 (
-      strings.splitString "/" (derivation {
-        name = "name";
-        builder = "builder";
-        system = "system";
-      })
-    );
-    expected = [
-      ""
-      "nix"
-      "store"
-    ];
+    expr = lib.dropEnd 1 (strings.splitString "/" dummyDerivation);
+    expected = strings.splitString "/" builtins.storeDir;
   };
 
   testSplitVersionSingle = {
@@ -841,7 +836,7 @@ runTests {
       in
       {
         storePath = isStorePath goodPath;
-        storePathDerivation = isStorePath (import ../.. { system = "x86_64-linux"; }).hello;
+        storePathDerivation = isStorePath dummyDerivation;
         storePathAppendix = isStorePath "${goodPath}/bin/python";
         nonAbsolute = isStorePath (concatStrings (tail (stringToCharacters goodPath)));
         asPath = isStorePath (/. + goodPath);
@@ -926,7 +921,7 @@ runTests {
   };
 
   testHasInfixDerivation = {
-    expr = hasInfix "hello" (import ../.. { system = "x86_64-linux"; }).hello;
+    expr = hasInfix "name" dummyDerivation;
     expected = true;
   };
 

lib/tests/test-with-nix.nix

@@ -18,8 +18,6 @@
 pkgs.runCommand "nixpkgs-lib-tests-nix-${nix.version}"
   {
     buildInputs = [
-      (import ./check-eval.nix)
-      (import ./fetchers.nix)
       (import ../path/tests {
         inherit pkgs;
       })
@@ -71,6 +69,12 @@ pkgs.runCommand "nixpkgs-lib-tests-nix-${nix.version}"
     echo "Running lib/tests/systems.nix"
     [[ $(nix-instantiate --eval --strict lib/tests/systems.nix | tee /dev/stderr) == '[ ]' ]];
 
+    echo "Running lib/tests/misc.nix"
+    [[ $(nix-instantiate --eval --strict lib/tests/misc.nix | tee /dev/stderr) == '[ ]' ]];
+
+    echo "Running lib/tests/fetchers.nix"
+    [[ $(nix-instantiate --eval --strict lib/tests/fetchers.nix | tee /dev/stderr) == '[ ]' ]];
+
     mkdir $out
     echo success > $out/${nix.version}
   ''