diff --git a/shard.lock b/shard.lock
index 3986ee0..2ce31b2 100644
--- a/shard.lock
+++ b/shard.lock
@@ -7,4 +7,3 @@ shards:
   version_from_shard:
     git: https://github.com/hugopl/version_from_shard.git
     version: 1.2.5
-
diff --git a/shards.nix b/shards.nix
index 8444749..603ff4c 100644
--- a/shards.nix
+++ b/shards.nix
@@ -9,4 +9,4 @@
     rev = "v1.2.5";
     sha256 = "0xizj0q4rd541rwjbx04cjifc2gfx4l5v6q2y7gmd0ndjmkgb8ik";
   };
-}
+}
\ No newline at end of file
diff --git a/spec/repo_spec.cr b/spec/repo_spec.cr
new file mode 100644
index 0000000..d1e6e8c
--- /dev/null
+++ b/spec/repo_spec.cr
@@ -0,0 +1,37 @@
+require "./spec_helper"
+
+Spectator.describe Repo do
+  context "commit" do
+    let(:with_commit) {
+      <<-EOF
+      git: https://github.com/cadmiumcr/transliterator.git
+      version: 0.1.0+git.commit.46c4c14594057dbcfaf27e7e7c8c164d3f0ce3f1
+      EOF
+    }
+
+    let(:repo) {
+      Crystal2Nix::Repo.new(Crystal2Nix::Shard.from_yaml(with_commit))
+    }
+
+    it "should have the commit as revision" do
+      expect(repo.rev).to eq("46c4c14594057dbcfaf27e7e7c8c164d3f0ce3f1")
+    end
+  end
+
+  context "explicit version" do
+    let(:with_version) {
+      <<-EOF
+      git: https://github.com/crystal-lang/json_mapping.cr.git
+      version: 0.1.1
+      EOF
+    }
+
+    let(:repo) {
+      Crystal2Nix::Repo.new(Crystal2Nix::Shard.from_yaml(with_version))
+    }
+
+    it "should prefix version references with a v" do
+      expect(repo.rev).to eq("v0.1.1")
+    end
+  end
+end
diff --git a/src/crystal2nix.cr b/src/crystal2nix.cr
index 0b9b558..68a2efb 100644
--- a/src/crystal2nix.cr
+++ b/src/crystal2nix.cr
@@ -10,4 +10,4 @@ require "./worker"
 
 module Crystal2Nix
   VersionFromShard.declare
-end
+end
\ No newline at end of file
diff --git a/src/data.cr b/src/data.cr
index 6e550c3..0ca2848 100644
--- a/src/data.cr
+++ b/src/data.cr
@@ -19,4 +19,4 @@ module Crystal2Nix
     property hg : String?
     property version : String
   end
-end
+end
\ No newline at end of file
diff --git a/src/repo.cr b/src/repo.cr
index c409271..a6d20ce 100644
--- a/src/repo.cr
+++ b/src/repo.cr
@@ -29,4 +29,4 @@ module Crystal2Nix
       @url.to_s
     end
   end
-end
+end
\ No newline at end of file
diff --git a/src/worker.cr b/src/worker.cr
index 0a98a60..36ddcb4 100644
--- a/src/worker.cr
+++ b/src/worker.cr
@@ -91,4 +91,4 @@ module Crystal2Nix
       puts "Processing completed successfully."
     end
   end
-end
+end
\ No newline at end of file