1 files changed, 93 insertions, 0 deletions
diff --git a/spec/ruby/core/enumerator/product_spec.rb b/spec/ruby/core/enumerator/product_spec.rb
new file mode 100644
index 0000000000..0acca6690e
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+++ b/spec/ruby/core/enumerator/product_spec.rb
@@ -0,0 +1,93 @@
+require_relative '../../spec_helper'
+
+ruby_version_is "3.2" do
+  describe "Enumerator.product" do
+    it "returns a Cartesian product of enumerators" do
+      enum = Enumerator.product(1..2, ["A", "B"])
+      enum.to_a.should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"]]
+    end
+
+    it "accepts a list of enumerators of any length" do
+      enum = Enumerator.product(1..2)
+      enum.to_a.should == [[1], [2]]
+
+      enum = Enumerator.product(1..2, ["A"])
+      enum.to_a.should == [[1, "A"], [2, "A"]]
+
+      enum = Enumerator.product(1..2, ["A"], ["B"])
+      enum.to_a.should == [[1, "A", "B"], [2, "A", "B"]]
+
+      enum = Enumerator.product(2..3, ["A"], ["B"], ["C"])
+      enum.to_a.should == [[2, "A", "B", "C"], [3, "A", "B", "C"]]
+    end
+
+    it "returns an enumerator with an empty array when no arguments passed" do
+      enum = Enumerator.product
+      enum.to_a.should == [[]]
+    end
+
+    it "returns an instance of Enumerator::Product" do
+      enum = Enumerator.product
+      enum.class.should == Enumerator::Product
+    end
+
+    it "accepts infinite enumerators and returns infinite enumerator" do
+      enum = Enumerator.product(1.., ["A", "B"])
+      enum.take(5).should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"], [3, "A"]]
+      enum.size.should == Float::INFINITY
+    end
+
+    it "accepts a block" do
+      elems = []
+      enum = Enumerator.product(1..2, ["X", "Y"]) { elems << _1 }
+
+      elems.should == [[1, "X"], [1, "Y"], [2, "X"], [2, "Y"]]
+    end
+
+    it "returns nil when a block passed" do
+      Enumerator.product(1..2) {}.should == nil
+    end
+
+    # https://bugs.ruby-lang.org/issues/19829
+    it "reject keyword arguments" do
+      -> {
+        Enumerator.product(1..3, foo: 1, bar: 2)
+      }.should raise_error(ArgumentError, "unknown keywords: :foo, :bar")
+    end
+
+    it "calls only #each_entry method on arguments" do
+      object = Object.new
+      def object.each_entry
+        yield 1
+        yield 2
+      end
+
+      enum = Enumerator.product(object, ["A", "B"])
+      enum.to_a.should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"]]
+    end
+
+    it "raises NoMethodError when argument doesn't respond to #each_entry" do
+      -> {
+        Enumerator.product(Object.new).to_a
+      }.should raise_error(NoMethodError, /undefined method [`']each_entry' for/)
+    end
+
+    it "calls #each_entry lazily" do
+      Enumerator.product(Object.new).should be_kind_of(Enumerator)
+    end
+
+    it "iterates through consuming enumerator elements only once" do
+      a = [1, 2, 3]
+      i = 0
+
+      enum = Enumerator.new do |y|
+        while i < a.size
+          y << a[i]
+          i += 1
+        end
+      end
+
+      Enumerator.product(['a', 'b'], enum).to_a.should == [["a", 1], ["a", 2], ["a", 3]]
+    end
+  end
+end