Add integration tests

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

tests/str.npp

@@ -0,0 +1,40 @@
+# Str type operator and function tests
+
+a = "asdf"
+b = 'This is a longer sentence'
+c = 'the quick brown fox jumped over the lazy dog\'s escaped characters'
+
+# to_str
+println("to_str")
+println(a)
+println(a.to_str())
+println(b)
+println(b.to_str())
+println(c)
+println(c.to_str())
+
+# to_repr
+println("to_repr")
+println("to_repr".to_repr())
+println(a.to_repr())
+println(b.to_repr())
+println(c.to_repr())
+println('I would\ninclude a\nmultiline string if\nit wasn\'t such a\npain to\ntest in the\n.expect file'.to_repr())
+
+# len
+println("len")
+println(a.len())
+println(b.len())
+println(c.len())
+
+# __add__
+println("__add__")
+println(a + a)
+println(a + a + a)
+println(a + b)
+println(b + a)
+# __mul__
+println("__mul__")
+println(a * 4)
+println(b * 5)
+println((a * 6).to_repr())