1 files changed, 117 insertions, 0 deletions
diff --git a/spec/ruby/core/io/buffer/shared_spec.rb b/spec/ruby/core/io/buffer/shared_spec.rb
new file mode 100644
index 0000000000..f2a638cf39
--- /dev/null
+++ b/spec/ruby/core/io/buffer/shared_spec.rb
@@ -0,0 +1,117 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#shared?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "with a buffer created with .new" do
+    it "is false for an internal buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::INTERNAL)
+      @buffer.shared?.should be_false
+    end
+
+    it "is false for a mapped buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+      @buffer.shared?.should be_false
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "is true for a regular mapping" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        @buffer.shared?.should be_true
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "is false for a private mapping" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+          @buffer.shared?.should be_false
+        end
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    it "is false for a buffer created without a block" do
+      @buffer = IO::Buffer.for("test")
+      @buffer.shared?.should be_false
+    end
+
+    it "is false for a buffer created with a block" do
+      IO::Buffer.for(+"test") do |buffer|
+        buffer.shared?.should be_false
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "is false" do
+        IO::Buffer.string(4) do |buffer|
+          buffer.shared?.should be_false
+        end
+      end
+    end
+  end
+
+  # Always false for slices
+  context "with a slice of a buffer" do
+    context "created with .new" do
+      it "is false when slicing an internal buffer" do
+        @buffer = IO::Buffer.new(4)
+        @buffer.slice.shared?.should be_false
+      end
+
+      it "is false when slicing a mapped buffer" do
+        @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+        @buffer.slice.shared?.should be_false
+      end
+    end
+
+    context "created with .map" do
+      it "is false when slicing a regular file-backed buffer" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+          @buffer.slice.shared?.should be_false
+        end
+      end
+
+      ruby_version_is "3.3" do
+        it "is false when slicing a private file-backed buffer" do
+          File.open(__FILE__, "r") do |file|
+            @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+            @buffer.slice.shared?.should be_false
+          end
+        end
+      end
+    end
+
+    context "created with .for" do
+      it "is false when slicing a buffer created without a block" do
+        @buffer = IO::Buffer.for("test")
+        @buffer.slice.shared?.should be_false
+      end
+
+      it "is false when slicing a buffer created with a block" do
+        IO::Buffer.for(+"test") do |buffer|
+          buffer.slice.shared?.should be_false
+        end
+      end
+    end
+
+    ruby_version_is "3.3" do
+      context "created with .string" do
+        it "is false" do
+          IO::Buffer.string(4) do |buffer|
+            buffer.slice.shared?.should be_false
+          end
+        end
+      end
+    end
+  end
+end