diff --git a/spec/tapioca/lockfile_diff_parser_spec.rb b/spec/tapioca/lockfile_diff_parser_spec.rb
new file mode 100644
index 000000000..6ca472764
--- /dev/null
+++ b/spec/tapioca/lockfile_diff_parser_spec.rb
@@ -0,0 +1,53 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "spec_helper"
+require "ruby_lsp/tapioca/lockfile_diff_parser"
+
+module RubyLsp
+  module Tapioca
+    class LockFileDiffParserSpec < Minitest::Spec
+      describe "#parse_added_or_modified_gems" do
+        it "parses added or modified gems from git diff" do
+          diff_output = <<~DIFF
+            +    new_gem (1.0.0)
+            +    updated_gem (2.0.0)
+            -    removed_gem (1.0.0)
+          DIFF
+
+          lockfile_parser = RubyLsp::Tapioca::LockfileDiffParser.new(diff_output)
+          assert_equal ["new_gem", "updated_gem"], lockfile_parser.added_or_modified_gems
+        end
+
+        it "is empty when there is no diff" do
+          diff_output = ""
+
+          lockfile_parser = RubyLsp::Tapioca::LockfileDiffParser.new(diff_output)
+          assert_empty lockfile_parser.added_or_modified_gems
+        end
+      end
+
+      describe "#parse_removed_gems" do
+        it "parses removed gems from git diff" do
+          diff_output = <<~DIFF
+            +    new_gem (1.0.0)
+            -    removed_gem (1.0.0)
+            -    outdated_gem (2.3.4)
+          DIFF
+
+          lockfile_parser = RubyLsp::Tapioca::LockfileDiffParser.new(diff_output)
+          assert_equal ["removed_gem", "outdated_gem"], lockfile_parser.removed_gems
+        end
+      end
+
+      it "handles gem names with awkward names" do
+        diff_output = <<~DIFF
+          -    my-gem_extra2 (1.0.0.beta1)
+        DIFF
+
+        lockfile_parser = RubyLsp::Tapioca::LockfileDiffParser.new(diff_output)
+        assert_equal ["my-gem_extra2"], lockfile_parser.removed_gems
+      end
+    end
+  end
+end