diff --git a/src/kdf.rs b/src/kdf.rs
index a44066c..ad842bd 100644
--- a/src/kdf.rs
+++ b/src/kdf.rs
@@ -59,18 +59,18 @@ pub(crate) fn derive_key(
 mod tests {
 	use crate::ikm::InputKeyMaterial;
 	use crate::KeyContext;
+	use std::num::NonZeroU64;
+
+	const TEST_RAW_IKM: &[u8] = &[
+		0x0a, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x7b, 0x85, 0x27, 0xef, 0xf2, 0xbd, 0x58,
+		0x9f, 0x6e, 0xb1, 0x7b, 0x71, 0xc3, 0x1e, 0xf6, 0xfd, 0x7f, 0x90, 0xdb, 0xc6, 0x43, 0xea,
+		0xe9, 0x9c, 0xa3, 0xb5, 0xee, 0xcc, 0xb6, 0xb6, 0x28, 0x6a, 0xbd, 0xe4, 0xd0, 0x65, 0x00,
+		0x00, 0x00, 0x00, 0x3d, 0x82, 0x6f, 0x8b, 0x00, 0x00, 0x00, 0x00, 0x00,
+	];
 
 	#[test]
-	fn derive_key() {
-		let ikm_raw = [
-			0x0a, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x7b, 0x85, 0x27, 0xef, 0xf2, 0xbd,
-			0x58, 0x9f, 0x6e, 0xb1, 0x7b, 0x71, 0xc3, 0x1e, 0xf6, 0xfd, 0x7f, 0x90, 0xdb, 0xc6,
-			0x43, 0xea, 0xe9, 0x9c, 0xa3, 0xb5, 0xee, 0xcc, 0xb6, 0xb6, 0x28, 0x6a, 0xbd, 0xe4,
-			0xd0, 0x65, 0x00, 0x00, 0x00, 0x00, 0x3d, 0x82, 0x6f, 0x8b, 0x00, 0x00, 0x00, 0x00,
-			0x00,
-		];
-		let ikm = InputKeyMaterial::from_bytes(&ikm_raw).unwrap();
-
+	fn derive_key_no_tp() {
+		let ikm = InputKeyMaterial::from_bytes(TEST_RAW_IKM).unwrap();
 		let ctx = KeyContext::from(["some", "context"]);
 		assert_eq!(
 			super::derive_key(&ikm, &ctx, None),
@@ -81,4 +81,54 @@ mod tests {
 			]
 		);
 	}
+
+	#[test]
+	fn derive_key_tp_0() {
+		let ikm = InputKeyMaterial::from_bytes(TEST_RAW_IKM).unwrap();
+		let ctx = KeyContext::from(["some", "context"]);
+		assert_eq!(
+			super::derive_key(&ikm, &ctx, Some(0)),
+			vec![
+				0xdc, 0x6c, 0x4b, 0xed, 0xef, 0x31, 0x2a, 0x83, 0x40, 0xc0, 0xee, 0xf4, 0xd7, 0xe5,
+				0xec, 0x2e, 0xcf, 0xda, 0x64, 0x0a, 0xb8, 0xb6, 0x89, 0xe4, 0x3c, 0x6e, 0xc2, 0x53,
+				0x0e, 0xaa, 0x38, 0x12
+			]
+		);
+	}
+
+	#[test]
+	fn derive_key_tp_42() {
+		let ikm = InputKeyMaterial::from_bytes(TEST_RAW_IKM).unwrap();
+		let ctx = KeyContext::from(["some", "context"]);
+		assert_eq!(
+			super::derive_key(&ikm, &ctx, Some(42)),
+			vec![
+				0xc7, 0xfb, 0x96, 0x6a, 0x15, 0xde, 0x5f, 0xfc, 0x66, 0xa6, 0xac, 0xda, 0x6b, 0x8e,
+				0xa3, 0x66, 0xd8, 0x70, 0x5b, 0x2f, 0xf9, 0x7f, 0xfb, 0x47, 0xb1, 0xa9, 0x93, 0xfc,
+				0xf5, 0x0b, 0x6d, 0x3c
+			]
+		);
+	}
+
+	#[test]
+	fn get_time_period() {
+		let test_vec = &[
+			// (periodicity, timestamp, reference value)
+			(1, 0, 0),
+			(1, 1, 1),
+			(1, 2, 2),
+			(1, 35015, 35015),
+			(16_777_216, 0, 0),
+			(16_777_216, 16_777_215, 0),
+			(16_777_216, 16_777_216, 1),
+			(16_777_216, 1_709_994_382, 101),
+		];
+		let mut ctx = KeyContext::from([]);
+		for (p, ts, ref_val) in test_vec {
+			let p = NonZeroU64::new(*p).unwrap();
+			ctx.set_periodicity(p);
+			let tp = ctx.get_time_period(*ts);
+			assert_eq!(tp, Some(*ref_val));
+		}
+	}
 }