diff --git a/source/dub/dub.d b/source/dub/dub.d
index fe5efe4..128b167 100644
--- a/source/dub/dub.d
+++ b/source/dub/dub.d
@@ -60,6 +60,7 @@
 
 	See_Also: `defaultRegistryURLs`
 */
+deprecated("This function wasn't intended for public use - open an issue with Dub if you need it")
 PackageSupplier[] defaultPackageSuppliers()
 {
 	logDiagnostic("Using dub registry url '%s'", defaultRegistryURLs[0]);
@@ -70,6 +71,7 @@
 
 	Allowed protocols are dub+http(s):// and maven+http(s)://.
 */
+deprecated("This function wasn't intended for public use - open an issue with Dub if you need it")
 PackageSupplier getRegistryPackageSupplier(string url)
 {
 	switch (url.startsWith("dub+", "mvn+", "file://"))
@@ -85,7 +87,7 @@
 	}
 }
 
-unittest
+deprecated unittest
 {
 	auto dubRegistryPackageSupplier = getRegistryPackageSupplier("dub+https://code.dlang.org");
 	assert(dubRegistryPackageSupplier.description.canFind(" https://code.dlang.org"));
@@ -320,19 +322,21 @@
 		{
 			ps ~= registry_var
 				.splitter(";")
-				.map!(url => getRegistryPackageSupplier(url))
+				.map!(url => this.makePackageSupplier(url))
 				.array;
 		}
 
 		if (skip < SkipPackageSuppliers.configured)
 		{
 			ps ~= m_config.registryUrls
-				.map!(url => getRegistryPackageSupplier(url))
+				.map!(url => this.makePackageSupplier(url))
 				.array;
 		}
 
 		if (skip < SkipPackageSuppliers.standard)
-			ps ~= defaultPackageSuppliers();
+			ps ~= new FallbackPackageSupplier(
+				defaultRegistryURLs.map!(url => this.makePackageSupplier(url))
+				.array);
 
 		return ps;
 	}
@@ -363,6 +367,34 @@
 			.length == 1);
 	}
 
+	/**
+	 * Instantiate a `PackageSupplier` according to a given URL
+	 *
+	 * This is a factory function for `PackageSupplier`. Child classes may
+	 * wish to override this to implement their own `PackageSupplier` logic,
+	 * be it by extending this method's ability or replacing it.
+	 *
+	 * Params:
+	 *	 url = The URL of the `PackageSupplier`.
+	 *
+	 * Returns:
+	 *	 A new instance of a `PackageSupplier`.
+	 */
+	protected PackageSupplier makePackageSupplier(string url) const
+	{
+		switch (url.startsWith("dub+", "mvn+", "file://"))
+		{
+		case 1:
+			return new RegistryPackageSupplier(URL(url[4..$]));
+		case 2:
+			return new MavenRegistryPackageSupplier(URL(url[4..$]));
+		case 3:
+			return new FileSystemPackageSupplier(NativePath(url[7..$]));
+		default:
+			return new RegistryPackageSupplier(URL(url));
+		}
+	}
+
 	/// ditto
 	deprecated("This is an implementation detail. " ~
 		"Use `packageSuppliers` to get the computed list of package " ~
diff --git a/source/dub/test/base.d b/source/dub/test/base.d
index 6f7c7b3..4e49876 100644
--- a/source/dub/test/base.d
+++ b/source/dub/test/base.d
@@ -8,6 +8,9 @@
 
 version (unittest):
 
+import std.array;
+public import std.algorithm;
+
 import dub.data.settings;
 public import dub.dependency;
 import dub.dub;
@@ -50,4 +53,72 @@
         // No-op
         return Settings.init;
     }
+
+    /// See `MockPackageSupplier` documentation for this class' implementation
+    protected override PackageSupplier makePackageSupplier(string url) const
+    {
+        return new MockPackageSupplier(url);
+    }
+}
+
+/**
+ * Implements a `PackageSupplier` that doesn't do any IO
+ *
+ * This `PackageSupplier` needs to be pre-loaded with `Package` it can
+ * find during the setup phase of the unittest.
+ */
+public class MockPackageSupplier : PackageSupplier
+{
+    /// Mapping of package name to packages, ordered by `Version`
+    protected Package[][string] pkgs;
+
+    /// URL this was instantiated with
+    protected string url;
+
+    ///
+    public this(string url)
+    {
+        this.url = url;
+    }
+
+    ///
+    public override @property string description()
+    {
+        return "unittest PackageSupplier for: " ~ this.url;
+    }
+
+    ///
+    public override Version[] getVersions(string package_id)
+    {
+        if (auto ppkgs = package_id in this.pkgs)
+            return (*ppkgs).map!(pkg => pkg.version_).array;
+        return null;
+    }
+
+    ///
+    public override void fetchPackage(
+        NativePath path, string package_id, in VersionRange dep, bool pre_release)
+    {
+        assert(0, this.url ~ " - fetchPackage not implemented for: " ~ package_id);
+    }
+
+    ///
+    public override Json fetchPackageRecipe(
+        string package_id, in VersionRange dep, bool pre_release)
+    {
+        import dub.recipe.json;
+
+        if (auto ppkgs = package_id in this.pkgs)
+            foreach_reverse (pkg; *ppkgs)
+                if ((!pkg.version_.isPreRelease || pre_release) &&
+                    dep.matches(pkg.version_))
+                    return toJson(pkg.recipe);
+        return Json.init;
+    }
+
+    ///
+    public override SearchResult[] searchPackages(string query)
+    {
+        assert(0, this.url ~ " - searchPackages not implemented for: " ~ query);
+    }
 }