Add tests for string methods that support UTF-8 already.

test/string/contains.wren

@@ -4,3 +4,7 @@ IO.print("something".contains("meth")) // expect: true
 IO.print("something".contains("some")) // expect: true
 IO.print("something".contains("ing"))  // expect: true
 IO.print("something".contains("math")) // expect: false
+
+// Non-ASCII.
+IO.print("søméthîng".contains("méth"))  // expect: true
+IO.print("søméthîng".contains("meth")) // expect: false

test/string/ends_with.wren

@@ -2,4 +2,8 @@ IO.print("abcd".endsWith("cd")) // expect: true
 IO.print("abcd".endsWith("abcde")) // expect: false
 IO.print("abcd".endsWith("abcd")) // expect: true
 IO.print("abcd".endsWith("f")) // expect: false
-IO.print("abcd".endsWith("")) // expect: true
+IO.print("abcd".endsWith("")) // expect: true
+
+// Non-ASCII.
+IO.print("søméthîng".endsWith("thîng"))  // expect: true
+IO.print("søméthîng".endsWith("thing")) // expect: false

test/string/equality.wren

@@ -17,3 +17,7 @@ IO.print("" != "abcd")      // expect: true
 // Not equal to other types.
 IO.print("1" != 1)        // expect: true
 IO.print("true" != true)  // expect: true
+
+// Non-ASCII.
+IO.print("vålue" == "value") // expect: false
+IO.print("vålue" == "vålue") // expect: true

test/string/index_of.wren

@@ -2,3 +2,8 @@ IO.print("abcd".indexOf("cd")) // expect: 2
 IO.print("abcd".indexOf("a")) // expect: 0
 IO.print("abcd".indexOf("abcde")) // expect: -1
 IO.print("abab".indexOf("ab")) // expect: 0
+
+// Non-ASCII. Note that it returns byte indices, not code points.
+IO.print("søméஃthîng".indexOf("e")) // expect: -1
+IO.print("søméஃthîng".indexOf("m")) // expect: 3
+IO.print("søméஃthîng".indexOf("thî")) // expect: 9

test/string/starts_with.wren

@@ -3,3 +3,7 @@ IO.print("abcd".startsWith("a")) // expect: true
 IO.print("abcd".startsWith("abcd")) // expect: true
 IO.print("abcd".startsWith("abcde")) // expect: false
 IO.print("abcd".startsWith("")) // expect: true
+
+// Non-ASCII.
+IO.print("søméthîng".startsWith("sømé"))  // expect: true
+IO.print("søméthîng".startsWith("some")) // expect: false