@@ -0,0 +1,65 @@
+// Unit tests for the pure helpers the phases of prepare_build share
+// (src/build/prepare/config.cpp and fetch.cpp): the --features request
+// grammar, the macro name a define entry names, the previous release's
+// reading of a flag element, and whether a git remote is local. Before the
+// decomposition of prepare.cppm these were internal to one 16,000-line unit
+// and reached only through whole builds; they are exported for this file.
+
+#include <gtest/gtest.h>
+
+import std;
+import mcpp.build.prepare;
+
+using Words = std::vector<std::string>;
+
+TEST(FeatureRequest, TokensSplitOnCommasAndSpaces) {
+    EXPECT_EQ(mcpp::build::feature_request_tokens("a,b c,,  d"), (Words{"a", "b", "c", "d"}));
+    EXPECT_TRUE(mcpp::build::feature_request_tokens("").empty());
+    EXPECT_TRUE(mcpp::build::feature_request_tokens(" , ").empty());
+}
+
+// #649 E8: a token with `/` opens a dependency's feature, so it is a forward
+// of the root and never one of the root's own features. A token with an
+// empty half stays whole, for the caller to name.
+TEST(FeatureRequest, ASlashTokenIsAForwardAndNotARootFeature) {
+    constexpr std::string_view request = "simd, dep/fast,  gpu,/x,y/";
+    EXPECT_EQ(mcpp::build::parse_feature_request(request), (Words{"simd", "gpu"}));
+    EXPECT_EQ(mcpp::build::feature_forward_request_tokens(request),
+              (Words{"dep/fast", "/x", "y/"}));
+}
+
+TEST(DefineName, IsTheTextBeforeTheFirstEquals) {
+    EXPECT_EQ(mcpp::build::define_name("NDEBUG"), "NDEBUG");
+    EXPECT_EQ(mcpp::build::define_name("VERSION=1"), "VERSION");
+    EXPECT_EQ(mcpp::build::define_name("EXPR=a=b"), "EXPR");
+    EXPECT_EQ(mcpp::build::define_name("=x"), "");
+}
+
+// The words an element reached the compiler as before flag_words: `$$` was a
+// literal dollar, and `${name}` or `$name` a ninja variable, empty on a
+// compile edge. A `defines` entry was read as `-D<entry>`.
+TEST(PreviousReleaseWords, ReadNinjaEscapesAndVariablesAsTheOldEdgeDid) {
+    EXPECT_EQ(mcpp::build::previous_release_words("-DA=x$$y", false), (Words{"-DA=x$y"}));
+    EXPECT_EQ(mcpp::build::previous_release_words("-DA=${v}z", false), (Words{"-DA=z"}));
+    EXPECT_EQ(mcpp::build::previous_release_words("-DA=$v", false), (Words{"-DA="}));
+    EXPECT_EQ(mcpp::build::previous_release_words("B=1", true), (Words{"-DB=1"}));
+}
+
+// A remote served by plain filesystem reads is local, so `--offline` keeps
+// building it; a scheme or scp-like syntax is remote. A Windows drive letter
+// has a colon but no `@`, so an existing `C:\repo` stays local.
+TEST(GitRemote, LocalMeansAFileUrlOrAnExistingPath) {
+    EXPECT_TRUE(mcpp::build::is_local_git_remote("file:///srv/repo.git"));
+    EXPECT_FALSE(mcpp::build::is_local_git_remote("https://github.com/x/y.git"));
+    EXPECT_FALSE(mcpp::build::is_local_git_remote("ssh://git@host/x.git"));
+    EXPECT_FALSE(mcpp::build::is_local_git_remote("git@github.com:x/y.git"));
+
+    namespace fs = std::filesystem;
+    const auto dir = fs::temp_directory_path()
+        / std::format("mcpp-prepare-helpers-{:x}", std::random_device{}());
+    fs::create_directories(dir);
+    EXPECT_TRUE(mcpp::build::is_local_git_remote(dir.string()));
+    EXPECT_FALSE(mcpp::build::is_local_git_remote((dir / "missing").string()));
+    std::error_code ec;
+    fs::remove_all(dir, ec);
+}