Add gas meter tests and some helpers unittest

tests/README.md

@@ -3,6 +3,5 @@
 TODO: more vm tests and fixtures!
 
 ```bash
-nim c tests/code_stream_test.nim
-./tests/code_stream_test
+./tests/test.sh
 ```

tests/gas_meter_test.nim

@@ -0,0 +1,86 @@
+import unittest, macros, strformat, strutils, sequtils, constants, opcode_values, errors, vm / gas_meter, bigints
+
+# TODO: quicktest
+# PS: parametrize can be easily immitated, but still quicktests would be even more useful
+
+proc gasMeters: seq[GasMeter] =
+  @[newGasMeter(10.i256), newGasMeter(100.i256), newGasMeter(999.i256)]
+
+macro all(element: untyped, handler: untyped): untyped =
+  let name = ident(&"{element.repr}s")
+  result = quote:
+    var res = `name`()
+    for `element` in res.mitems:
+      `handler`
+
+# @pytest.mark.parametrize("value", (0, 10))
+# def test_start_gas_on_instantiation(value):
+#     meter = GasMeter(value)
+#     assert meter.start_gas == value
+#     assert meter.gas_remaining == value
+#     assert meter.gas_refunded == 0
+
+
+# @pytest.mark.parametrize("value", (-1, 2**256, 'a'))
+# def test_instantiation_invalid_value(value):
+#     with pytest.raises(ValidationError):
+#         GasMeter(value)
+
+
+# @pytest.mark.parametrize("amount", (0, 1, 10))
+# def test_consume_gas(gas_meter, amount):
+#     gas_meter.consume_gas(amount, "reason")
+#     assert gas_meter.gas_remaining == gas_meter.start_gas - amount
+
+
+# @pytest.mark.parametrize("amount", (0, 1, 99))
+# def test_return_gas(gas_meter, amount):
+#     gas_meter.return_gas(amount)
+#     assert gas_meter.gas_remaining == (gas_meter.start_gas + amount)
+
+# @pytest.mark.parametrize("amount", (0, 1, 99))
+# def test_refund_gas(gas_meter, amount):
+#     gas_meter.refund_gas(amount)
+#     assert gas_meter.gas_refunded == amount
+
+
+suite "gasMeter":
+  test "consume rejects negative":
+    all(gasMeter):
+      expect(ValidationError):
+        gasMeter.consumeGas(-1.i256, "independent")
+
+  test "return rejects negative":
+    all(gasMeter):
+      expect(ValidationError):
+        gasMeter.returnGas(-1.i256)
+
+  test "refund rejects negative":
+    all(gasMeter):
+      expect(ValidationError):
+        gasMeter.returnGas(-1.i256)
+
+  # TODO: -0/+0 
+  test "consume spends":
+    all(gasMeter):
+      check(gasMeter.gasRemaining == gasMeter.startGas)
+      let consume = gasMeter.startGas
+      gasMeter.consumeGas(consume, "0")
+      check(gasMeter.gasRemaining == gasMeter.startGas - consume)
+
+  test "consume errors":
+    all(gasMeter):
+      check(gasMeter.gasRemaining == gasMeter.startGas)
+      expect(OutOfGas):
+        gasMeter.consumeGas(gasMeter.startGas + 1.i256, "")
+
+  test "return refund works correctly":
+    all(gasMeter):
+      check(gasMeter.gasRemaining == gasMeter.startGas)
+      check(gasMeter.gasRefunded == 0)
+      gasMeter.consumeGas(5.i256, "")
+      check(gasMeter.gasRemaining == gasMeter.startGas - 5.i256)
+      gasMeter.returnGas(5.i256)
+      check(gasMeter.gasRemaining == gasMeter.startGas)
+      gasMeter.refundGas(5.i256)
+      check(gasMeter.gasRefunded == 5.i256)

tests/test.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+nim c tests/code_stream_test.nim
+nim c tests/gas_meter_test.nim
+./tests/code_stream_test
+./tests/gas_meter_test