cleanup tests/stdlib/tstring.nim (#17158)

* cleanup tests/stdlib/tstring.nim

* cleanup tests/stdlib/tstring.nim

* cleanup rest of test

tests/stdlib/tstring.nim

@@ -2,10 +2,24 @@ discard """
   targets: "c cpp js"
 """
 
-const characters = "abcdefghijklmnopqrstuvwxyz"
-const numbers = "1234567890"
+from std/sequtils import toSeq, map
+from std/sugar import `=>`
+
+proc tester[T](x: T) =
+  let test = toSeq(0..4).map(i => newSeq[int]())
+  doAssert $test == "@[@[], @[], @[], @[], @[]]"
+
+func reverse*(a: string): string =
+  result = a
+  for i in 0 ..< a.len div 2:
+    swap(result[i], result[^(i + 1)])
+
+proc main() =
+  block: # ..
+    const
+      characters = "abcdefghijklmnopqrstuvwxyz"
+      numbers = "1234567890"
 
-proc test_string_slice() =
     # test "slice of length == len(characters)":
     # replace characters completely by numbers
     var s: string
@@ -56,8 +70,7 @@ proc test_string_slice() =
       doAssertRaises(IndexDefect):
         discard s[0..999]
 
-
-proc test_string_cmp() =
+  block: # ==, cmp
     let world = "hello\0world"
     let earth = "hello\0earth"
     let short = "hello\0"
@@ -76,33 +89,10 @@ proc test_string_cmp() =
     doAssert cmp(world, hello) > 0
     doAssert cmp(world, goodbye) > 0
 
-
-#--------------------------
-# bug #7816
-import sugar
-import sequtils
-
-proc tester[T](x: T) =
-  let test = toSeq(0..4).map(i => newSeq[int]())
-  doAssert $test == "@[@[], @[], @[], @[], @[]]"
-
-
-
-# #14497 
-func reverse*(a: string): string =
-  result = a
-  for i in 0 ..< a.len div 2:
-    swap(result[i], result[^(i + 1)])
-
-
-proc main() =
-  # xxx put all tests here to test in VM and RT
-  test_string_slice()
-  test_string_cmp()
-
+  block: # bug #7816
     tester(1)
 
-  block: # reverse
+  block: # bug #14497, reverse
     doAssert reverse("hello") == "olleh"
 
   block: # len, high
@@ -123,16 +113,10 @@ proc main() =
     doAssert "".cstring.len == 0
     doAssert "".cstring.high == -1
 
+    block: # bug #16674
       var c: cstring = nil
-    template impl() =
       doAssert c.len == 0
       doAssert c.high == -1
-    when defined js:
-      when nimvm: impl()
-      else:
-        # xxx pending bug #16674
-        discard
-    else: impl()
 
 static: main()
 main()