implement most of the missing functions for sic simulator

sim/test/sim_test.gleam

@@ -1,4 +1,6 @@
 import gleeunit
+import sim/device
+import sim/memory
 
 pub fn main() -> Nil {
   gleeunit.main()
@@ -11,3 +13,35 @@ pub fn hello_world_test() {
 
   assert greeting == "Hello, Joe!"
 }
+
+pub fn pad_test() {
+  assert <<1, 2, 3, 0>> == memory.pad_to_length(<<1, 2, 3>>, 32)
+}
+
+pub fn insert_test() {
+  assert <<1, 2, 3, 4>> == memory.insert_at(<<1, 2, 3>>, 3, <<4>>)
+  assert <<1, 2, 3, 0, 5>> == memory.insert_at(<<1, 2, 3>>, 4, <<5>>)
+  assert <<1, 67, 3>> == memory.insert_at(<<1, 2, 3>>, 1, <<67>>)
+}
+
+pub fn open_test() {
+  let d0 = device.open("0")
+  device.close(d0)
+}
+
+pub fn test_device_test() {
+  let d1 = device.open("1")
+  assert <<>> == device.read(d1).0
+  let d1 = device.test_device(d1)
+  assert d1.has_data == True
+  let #(char, d1) = device.read(d1)
+  assert <<"a">> == char
+  assert d1.has_data == False
+  assert <<>> == device.read(d1).0
+  device.close(d1)
+
+  let d0 = device.open("0")
+  let d0 = device.test_device(d0)
+  assert d0.has_data == False
+  device.close(d0)
+}