Switch to RSpec

Gemfile.lock

@@ -4,6 +4,7 @@ GEM
     anyflake (0.0.1)
     ast (2.4.2)
     base64 (0.2.0)
+    diff-lcs (1.5.1)
     json (2.7.2)
     jwt (2.8.2)
       base64
@@ -20,7 +21,6 @@ GEM
     parser (3.3.3.0)
       ast (~> 2.4.1)
       racc
-    power_assert (2.0.3)
     prism (0.30.0)
     puma (6.4.2)
       nio4r (~> 2.0)
@@ -42,6 +42,19 @@ GEM
     regexp_parser (2.9.2)
     rexml (3.3.0)
       strscan
+    rspec (3.13.0)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-core (3.13.0)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-support (3.13.1)
     rubocop (1.64.1)
       json (~> 2.3)
       language_server-protocol (>= 3.17.0)
@@ -91,8 +104,6 @@ GEM
       lint_roller (~> 1.1)
       rubocop-performance (~> 1.21.0)
     strscan (3.1.0)
-    test-unit (3.6.2)
-      power_assert
     tilt (2.3.0)
     ulid (1.4.0)
     unicode-display_width (2.5.0)
@@ -114,12 +125,12 @@ DEPENDENCIES
   rack-test
   rackup
   rbs
+  rspec
   rubocop
   ruby-lsp
   sinatra
   sinatra-contrib
   standard
-  test-unit
   ulid
   uuid7