diff --git a/build.zig b/build.zig
index ccedb37d83760f9d9fdda9b777be173e015e86a9..039ebe29e6dc3110555da0db2bc84f0a42a813fe 100644
--- a/build.zig
+++ b/build.zig
@@ -23,6 +23,15 @@ pub fn build(b: *std.Build) void {
     const run_step = b.step("run", "Run the app");
     run_step.dependOn(&run_cmd.step);
 
+    const tests = b.addTest(.{
+        .root_source_file = b.path("./test.zig"),
+        .target = target,
+        .optimize = mode,
+    });
+    deps.addAllTo(tests);
+
+    const tests_run = b.addRunArtifact(tests);
+
     const test_step = b.step("test", "dummy test step to pass CI checks");
-    _ = test_step;
+    test_step.dependOn(&tests_run.step);
 }
diff --git a/test.zig b/test.zig
new file mode 100644
index 0000000000000000000000000000000000000000..5f33a5984c23587be5868ceb541f6305f2c9dc41
--- /dev/null
+++ b/test.zig
@@ -0,0 +1,30 @@
+const std = @import("std");
+const string = []const u8;
+const ulid = @import("ulid");
+
+// zig fmt: off
+test { try ensureFromTo("001HX7QW7K2PP61CS28B4YF00X"); }
+test { try ensureFromTo("0015KMZ1NDDFP4WRWSVA31N0CD"); }
+test { try ensureFromTo("0015MFYM13K180VCNCACTFRJAB"); }
+test { try ensureFromTo("0015RMHR0WVSCBE4CJWKPCC4GJ"); }
+test { try ensureFromTo("0017NSY29QD0YYPB0H0W5GQJQX"); }
+test { try ensureFromTo("0017TZRGVZYHK9C26FK5AP3HTG"); }
+test { try ensureFromTo("0017Y302CVXHJABSPHNNEBE0R7"); }
+test { try ensureFromTo("00183KTME6PJZ773Q9A1BWFJ3X"); }
+test { try ensureFromTo("0018ZPQ92P0NDDKNVB3PBW7D18"); }
+test { try ensureFromTo("00193A6YMTQR01XTY757XRRJKE"); }
+test { try ensureFromTo("0019ABB5M0YK71B4ATA90A8F81"); }
+test { try ensureFromTo("0019GFR7YK5HNTFPS2BAQNG0PX"); }
+test { try ensureFromTo("001A2YPKW942R97BXRAJG2BD7S"); }
+test { try ensureFromTo("001C38D808VW1EG3JS6XJHT4EQ"); }
+test { try ensureFromTo("001C9DSQ8SC6SVEVHFK09XBFTC"); }
+test { try ensureFromTo("001DEJXKVPDV7BZT1Q80ZEN2PF"); }
+test { try ensureFromTo("001F1Z79BCKADWYPDCMZ8B8G0G"); }
+// zig fmt: on
+
+fn ensureFromTo(before: string) !void {
+    const alloc = std.heap.page_allocator;
+    const ul = try ulid.ULID.parse(alloc, before);
+    const after = try ul.toString(alloc);
+    try std.testing.expectEqualStrings(before, after);
+}