implements the list group function (#400)

2 files changed, 27 insertions, 0 deletions

diff --git a/test/gleam/list_test.gleam b/test/gleam/list_test.gleam
index ce865e4..68a02f8 100644
--- a/test/gleam/list_test.gleam
+++ b/test/gleam/list_test.gleam
@@ -1,6 +1,7 @@
 import gleam/float
 import gleam/int
 import gleam/list
+import gleam/map
 import gleam/should
 
 if erlang {
@@ -94,6 +95,29 @@ pub fn rest_test() {
   |> should.equal(Error(Nil))
 }
 
+pub fn group_test() {
+  [Ok(10), Error("Wrong"), Ok(200), Ok(1)]
+  |> list.group(fn(i) {
+    case i {
+      Ok(_) -> "Successful"
+      Error(_) -> "Failed"
+    }
+  })
+  |> should.equal(
+    map.new()
+    |> map.insert("Failed", [Error("Wrong")])
+    |> map.insert("Successful", [Ok(1), Ok(200), Ok(10)]),
+  )
+
+  list.group([1, 2, 3, 4, 5], fn(i) { i - i / 3 * 3 })
+  |> should.equal(
+    map.new()
+    |> map.insert(0, [3])
+    |> map.insert(1, [4, 1])
+    |> map.insert(2, [5, 2]),
+  )
+}
+
 pub fn filter_test() {
   []
   |> list.filter(fn(_) { True })
diff --git a/test/gleam/option_test.gleam b/test/gleam/option_test.gleam
index ed0e61a..11bbe3e 100644
--- a/test/gleam/option_test.gleam
+++ b/test/gleam/option_test.gleam
@@ -5,6 +5,9 @@ pub fn all_test() {
   option.all([Some(1), Some(2), Some(3)])
   |> should.equal(Some([1, 2, 3]))
 
+  option.all([])
+  |> should.equal(Some([]))
+
   option.all([Some(1), None, Some(3)])
   |> should.equal(None)
 }