More test coverage for Enum for non-list inputs (#14471)

* Add tests for Enum.max/2 with empty fallback

* Add tests for Enum.min/2 with empty fallback

* Add tests for Enum.random/1 with streams or empty range

* Add tests for Enum.reduce/3 for streams & maps

Author: sabiwara

lib/elixir/test/elixir/enum_test.exs

@@ -562,6 +562,11 @@ defmodule EnumTest do
     end
   end
 
+  test "max/2 with empty fallback" do
+    assert Enum.max([], fn -> 0 end) === 0
+    assert Enum.max([1, 2], fn -> 0 end) === 2
+  end
+
   test "max/2 with stable sorting" do
     assert Enum.max([1, 1.0], &>=/2) === 1
     assert Enum.max([1.0, 1], &>=/2) === 1.0
@@ -646,6 +651,11 @@ defmodule EnumTest do
     end
   end
 
+  test "min/2 with empty fallback" do
+    assert Enum.min([], fn -> 0 end) === 0
+    assert Enum.min([1, 2], fn -> 0 end) === 1
+  end
+
   test "min/2 with stable sorting" do
     assert Enum.min([1, 1.0], &<=/2) === 1
     assert Enum.min([1.0, 1], &<=/2) === 1.0
@@ -820,6 +830,21 @@ defmodule EnumTest do
     assert Enum.random([1, 2, 3, 4, 5]) == 3
   end
 
+  test "random/1 with streams" do
+    random_stream = fn list -> list |> Stream.map(& &1) |> Enum.random() end
+
+    assert_raise Enum.EmptyError, fn -> random_stream.([]) end
+    assert random_stream.([1]) == 1
+
+    seed = {1406, 407_414, 139_258}
+    :rand.seed(:exsss, seed)
+
+    assert random_stream.([1, 2]) == 2
+    assert random_stream.([1, 2, 3]) == 3
+    assert random_stream.([1, 2, 3, 4]) == 1
+    assert random_stream.([1, 2, 3, 4, 5]) == 3
+  end
+
   test "reduce/2" do
     assert Enum.reduce([1, 2, 3], fn x, acc -> x + acc end) == 6
 
@@ -837,6 +862,13 @@ defmodule EnumTest do
     assert Enum.reduce([1, 2, 3], 1, fn x, acc -> x + acc end) == 7
   end
 
+  test "reduce/3 with streams" do
+    reduce_stream = fn list, acc, fun -> list |> Stream.map(& &1) |> Enum.reduce(acc, fun) end
+
+    assert reduce_stream.([], 1, fn x, acc -> x + acc end) == 1
+    assert reduce_stream.([1, 2, 3], 1, fn x, acc -> x + acc end) == 7
+  end
+
   test "reduce_while/3" do
     assert Enum.reduce_while([1, 2, 3], 1, fn i, acc -> {:cont, acc + i} end) == 7
     assert Enum.reduce_while([1, 2, 3], 1, fn _i, acc -> {:halt, acc} end) == 1
@@ -2023,6 +2055,11 @@ defmodule EnumTest.Range do
     assert_raise Enum.EmptyError, fn -> Enum.max(1..0//1) end
   end
 
+  test "max/2 with empty fallback" do
+    assert Enum.max(.., fn -> 0 end) === 0
+    assert Enum.max(1..2, fn -> 0 end) === 2
+  end
+
   test "max_by/2" do
     assert Enum.max_by(1..1, fn x -> :math.pow(-2, x) end) == 1
     assert Enum.max_by(1..3, fn x -> :math.pow(-2, x) end) == 2
@@ -2061,6 +2098,11 @@ defmodule EnumTest.Range do
     assert_raise Enum.EmptyError, fn -> Enum.min(1..0//1) end
   end
 
+  test "min/2 with empty fallback" do
+    assert Enum.min(.., fn -> 0 end) === 0
+    assert Enum.min(1..2, fn -> 0 end) === 1
+  end
+
   test "min_by/2" do
     assert Enum.min_by(1..1, fn x -> :math.pow(-2, x) end) == 1
     assert Enum.min_by(1..3, fn x -> :math.pow(-2, x) end) == 3
@@ -2112,6 +2154,8 @@ defmodule EnumTest.Range do
 
     assert Enum.random(1..10//2) == 7
     assert Enum.random(1..10//2) == 5
+
+    assert_raise Enum.EmptyError, fn -> Enum.random(..) end
   end
 
   test "reduce/2" do
@@ -2646,6 +2690,11 @@ defmodule EnumTest.Map do
       Enum.slice(map, 0, 0.99)
     end
   end
+
+  test "reduce/3" do
+    assert Enum.reduce(%{}, 1, fn x, acc -> x + acc end) == 1
+    assert Enum.reduce(%{a: 1, b: 2}, 1, fn {_, x}, acc -> x + acc end) == 4
+  end
 end
 
 defmodule EnumTest.SideEffects do