Remove specs for rb_fstring()

* It is a private function and the specs are redundant with specs for
  rb_str_to_interned_str().

Author: eregon

spec/ruby/optional/capi/ext/string_spec.c

@@ -51,12 +51,6 @@ VALUE string_spec_rb_str_set_len_RSTRING_LEN(VALUE self, VALUE str, VALUE len) {
   return INT2FIX(RSTRING_LEN(str));
 }
 
-VALUE rb_fstring(VALUE str); /* internal.h, used in ripper */
-
-VALUE string_spec_rb_str_fstring(VALUE self, VALUE str) {
-  return rb_fstring(str);
-}
-
 VALUE string_spec_rb_str_buf_new(VALUE self, VALUE len, VALUE str) {
   VALUE buf;
 
@@ -597,7 +591,6 @@ void Init_string_spec(void) {
   VALUE cls = rb_define_class("CApiStringSpecs", rb_cObject);
   rb_define_method(cls, "rb_cstr2inum", string_spec_rb_cstr2inum, 2);
   rb_define_method(cls, "rb_cstr_to_inum", string_spec_rb_cstr_to_inum, 3);
-  rb_define_method(cls, "rb_fstring", string_spec_rb_str_fstring, 1);
   rb_define_method(cls, "rb_str2inum", string_spec_rb_str2inum, 2);
   rb_define_method(cls, "rb_str_append", string_spec_rb_str_append, 2);
   rb_define_method(cls, "rb_str_buf_new", string_spec_rb_str_buf_new, 2);

spec/ruby/optional/capi/string_spec.rb

@@ -498,25 +498,6 @@ def inspect
     end
   end
 
-  describe "rb_fstring" do
-    it 'returns self if the String is frozen' do
-      input  = 'foo'.freeze
-      output = @s.rb_fstring(input)
-
-      output.should equal(input)
-      output.should.frozen?
-    end
-
-    it 'returns a frozen copy if the String is not frozen' do
-      input  = 'foo'
-      output = @s.rb_fstring(input)
-
-      output.should.frozen?
-      output.should_not equal(input)
-      output.should == 'foo'
-    end
-  end
-
   describe "rb_str_subseq" do
     it "returns a byte-indexed substring" do
       str = "\x00\x01\x02\x03\x04".force_encoding("binary")