1 files changed, 34 insertions, 0 deletions
diff --git a/test/gleam/pair_test.gleam b/test/gleam/pair_test.gleam
index 54a12af..5dd2690 100644
--- a/test/gleam/pair_test.gleam
+++ b/test/gleam/pair_test.gleam
@@ -26,3 +26,37 @@ pub fn swap_test() {
   |> pair.swap
   |> expect.equal(_, pair.Pair("2", 1))
 }
+
+pub fn map_first_test() {
+    let inc = fn(a) {
+        a + 1
+    }
+    pair.map_first(pair.Pair(1, 2), inc)
+    |> expect.equal(_, pair.Pair(2, 2))
+
+    pair.map_first(pair.Pair(8,2), inc)
+    |> expect.equal(_, pair.Pair(9, 2))
+
+    pair.map_first(pair.Pair(0,-2), inc)
+    |> expect.equal(_, pair.Pair(1, -2))
+
+    pair.map_first(pair.Pair(-10, 20), inc)
+    |> expect.equal(_, pair.Pair(-9, 20))
+}
+
+pub fn map_second_test() {
+    let dec = fn(a) {
+        a - 1
+    }
+    pair.map_second(pair.Pair(1, 2), dec)
+    |> expect.equal(_, pair.Pair(1, 1))
+
+    pair.map_second(pair.Pair(8,2), dec)
+    |> expect.equal(_, pair.Pair(8, 1))
+
+    pair.map_second(pair.Pair(0,-2), dec)
+    |> expect.equal(_, pair.Pair(0, -3))
+
+    pair.map_second(pair.Pair(-10, 20), dec)
+    |> expect.equal(_, pair.Pair(-10, 19))
+}