From fcf19a59b936d4129c1f6674570853f12c1639cf Mon Sep 17 00:00:00 2001
From: "Z. Charles Dziura" <zachary@dziura.email>
Date: Fri, 24 Jun 2022 16:53:25 -0400
Subject: [PATCH] Add test for ulid generator

Compares against the `ulid-rs` crate.
---
 Cargo.lock  | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 Cargo.toml  |  3 +++
 src/main.rs | 18 +++++++++++++++
 3 files changed, 87 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 98af7b1..e6358b5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -66,6 +66,21 @@ dependencies = [
  "getrandom",
 ]
 
+[[package]]
+name = "num_threads"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2819ce041d2ee131036f4fc9d6ae7ae125a3a40e97ba64d04fe799ad9dabbb44"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "ppv-lite86"
+version = "0.2.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eb9f9e6e233e5c4a35559a617bf40a4ec447db2e84c20b55a6f83167b7e57872"
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.40"
@@ -84,6 +99,36 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "rand"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d34f1408f55294453790c48b2f1ebbb1c5b4b7563eb1f418bcfcfdbb06ebb4e7"
+dependencies = [
+ "getrandom",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.98"
@@ -95,11 +140,32 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "time"
+version = "0.3.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72c91f41dcb2f096c05f0873d667dceec1087ce5bcf984ec8ffb19acddbb3217"
+dependencies = [
+ "libc",
+ "num_threads",
+]
+
+[[package]]
+name = "ulid"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3be932d774bfad49722da2c4915ac7cc77b77dd223890739a0240de2b2a15957"
+dependencies = [
+ "rand",
+ "time",
+]
+
 [[package]]
 name = "ulid-bin"
 version = "0.1.0"
 dependencies = [
  "nanorand",
+ "ulid",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index d5e63ba..a7bcb2c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,6 +9,9 @@ license = "GPL-3.0-or-later"
 [dependencies]
 nanorand = { version = "0.7", features = ["getrandom", "std", "chacha"] }
 
+[dev-dependencies]
+ulid = "0.6"
+
 [[bin]]
 name = "ulid"
 path = "src/main.rs"
diff --git a/src/main.rs b/src/main.rs
index c0b596b..d1e086a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -59,3 +59,21 @@ fn format_id(id: u128) -> String {
 
     formatted_id
 }
+
+#[cfg(test)]
+mod tests {
+    use ulid::Ulid;
+
+    use super::combine_bits;
+
+    const TIMESTAMP: u128 = 0x1F3FFFFFC17; // One millisecond less than the max unix timestamp.
+    const RANDOM_BITS: u128 = 0x995ca2c6bcf9f1807ffe2b18adb6b77d; // Chosen by fair die roll. Guaranteed to be random.
+
+    #[test]
+    fn test_generates_same_ulid_as_ulid_crate_given_same_inputs() {
+        let our_ulid = combine_bits(TIMESTAMP, RANDOM_BITS);
+        let external_ulid: u128 = Ulid::from_parts(TIMESTAMP as u64, RANDOM_BITS).into();
+
+        assert_eq!(our_ulid, external_ulid);
+    }
+}