Add some end-to-end tests for the suggestions

tests/local.mk

@@ -92,8 +92,9 @@ nix_tests = \
   bash-profile.sh \
   pass-as-file.sh \
   describe-stores.sh \
-  store-ping.sh \
-  nix-profile.sh
+  nix-profile.sh \
+  suggestions.sh \
+  store-ping.sh
 
 ifeq ($(HAVE_LIBCPUID), 1)
 	nix_tests += compute-levels.sh

tests/suggestions.sh

@@ -0,0 +1,36 @@
+source common.sh
+
+clearStore
+
+cd "$TEST_HOME"
+
+cat <<EOF > flake.nix
+{
+    outputs = a: {
+       packages.$system = {
+         foo = 1;
+         fo1 = 1;
+         fo2 = 1;
+         fooo = 1;
+         foooo = 1;
+         fooooo = 1;
+         fooooo1 = 1;
+         fooooo2 = 1;
+         fooooo3 = 1;
+         fooooo4 = 1;
+         fooooo5 = 1;
+         fooooo6 = 1;
+       };
+    };
+}
+EOF
+
+# Probable typo in the requested attribute path. Suggest some close possibilities
+NIX_BUILD_STDERR_WITH_SUGGESTIONS=$(! nix build .\#fob 2>&1 1>/dev/null)
+[[ "$NIX_BUILD_STDERR_WITH_SUGGESTIONS" =~ "Did you mean one of fo1, fo2, foo or fooo?" ]] || \
+    fail "The nix build stderr should suggest the three closest possiblities"
+
+# None of the possible attributes is close to `bar`, so shouldn’t suggest anything
+NIX_BUILD_STDERR_WITH_NO_CLOSE_SUGGESTION=$(! nix build .\#bar 2>&1 1>/dev/null)
+[[ ! "$NIX_BUILD_STDERR_WITH_NO_CLOSE_SUGGESTION" =~ "Did you mean" ]] || \
+    fail "The nix build stderr shouldn’t suggest anything if there’s nothing relevant to suggest"