Move /src/test to /tests

tests/ui/array-slice-vec/slice-mut.rs

@@ -0,0 +1,12 @@
+// Test mutability and slicing syntax.
+
+fn main() {
+    let x: &[isize] = &[1, 2, 3, 4, 5];
+    // Immutable slices are not mutable.
+
+    let y: &mut[_] = &x[2..4];
+    //~^ ERROR mismatched types
+    //~| expected mutable reference `&mut [_]`
+    //~| found reference `&[isize]`
+    //~| types differ in mutability
+}