JS: move more test to box tests

js/js.translator/testData/box/number/longUnaryOperations.kt

@@ -0,0 +1,31 @@
+package foo
+
+fun box(): String {
+
+    var x: Long = 2L
+    x++
+    assertEquals(3L, x)
+    ++x
+    assertEquals(4L, x)
+
+    var y = x++
+    assertEquals(4L, y)
+    assertEquals(5L, x)
+
+    y = ++x
+    assertEquals(6L, y)
+    assertEquals(6L, x)
+
+    x--
+    assertEquals(5L, x)
+    --x
+    assertEquals(4L, x)
+
+    y = +x
+    assertEquals(4L, y)
+
+    y = -x
+    assertEquals(-4L, y)
+
+    return "OK"
+}