diff --git a/.gitignore b/.gitignore
index 05b1eb201..c85aefea6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,2 @@
 nimcache/
-runner
-*_test
+build/
diff --git a/.travis.yml b/.travis.yml
index 2f58ed871..c980ec6d6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,7 +2,7 @@ sudo: required
 services:
   - docker
 before_install:
-  - docker pull yglukhov/nim-base
+  - docker pull statusteam/nim-base
 script:
-  - docker run yglukhov/nim-base nim --version
-  - docker run -v "$(pwd):/project" -w /project yglukhov/nim-base /bin/bash -c "nimble install -y && ./tests/build_test.sh && ./tests/test.sh"
+  - docker run -v "$(pwd):/project" -w /project statusteam/nim-base nim --version
+  - docker run -v "$(pwd):/project" -w /project statusteam/nim-base sh -c "nimble refresh && nimble test"
diff --git a/nimbus.nimble b/nimbus.nimble
index d516bdd5a..e72f3e09d 100644
--- a/nimbus.nimble
+++ b/nimbus.nimble
@@ -7,10 +7,20 @@ description   = "An Ethereum 2.0 Sharding Client for Resource-Restricted Devices
 license       = "Apache License 2.0"
 skipDirs      = @["tests"]
 
-requires "nim >= 0.17.0",
+requires "nim >= 0.18.1",
          "https://github.com/status-im/nim-keccak-tiny.git >= 0.1.0",
-         "https://github.com/alehander42/nim-rlp.git#fix-ordinal",
-         "https://github.com/status-im/nim-ttmath >= 0.5.0"
-
+         "https://github.com/alehander42/nim-rlp#fix-ordinal", #TODO switching to the Status repo throws: "Error: undeclared identifier: 'Range'"
+         "https://github.com/status-im/nim-ttmath#master"
 
+proc test(name: string, lang = "cpp") =
+  if not dirExists "build":
+    mkDir "build"
+  if not dirExists "nimcache":
+    mkDir "nimcache"
+  --run
+  --nimcache: "nimcache"
+  switch("out", ("./build/" & name))
+  setCommand lang, "tests/" & name & ".nim"
 
+task test, "Run tests":
+  test "all_tests"
diff --git a/src/vm/value.nim b/src/vm/value.nim
index e03664928..f93bb5bfb 100644
--- a/src/vm/value.nim
+++ b/src/vm/value.nim
@@ -8,10 +8,18 @@ type
   Value* = ref object
     case kind*: ValueKind:
     of VInt:
-      i*: Int256
+      Fi: array[32, byte] #Int256
     of VBinary:
       b*: seq[byte]
 
+# TODO: The Int256 value is stored as array[32, byte], and we bitcast it
+# back and forth. This is a hacky workaround for the problem that clang
+# doesn't let you store ttmath types inside nim variant types (unions). Things
+# should get better when we switch to mpint.
+
+proc i*(v: Value): Int256 {.inline.} =
+  cast[ptr Int256](unsafeAddr v.Fi)[]
+
 proc `$`*(value: Value): string =
   case value.kind:
   of VInt:
@@ -19,23 +27,16 @@ proc `$`*(value: Value): string =
   of VBinary:
     &"Binary({value.b})"
 
-proc vint*(i: int): Value =
-  Value(kind: VInt, i: i.int256)
+proc toArr(i: Int256): array[32, byte] {.inline.} =
+  cast[ptr array[32, byte]](unsafeAddr i)[]
 
 proc vint*(i: Int256): Value =
-  Value(kind: VInt, i: i)
+  Value(kind: VInt, Fi: i.toArr)
+
+proc vint*(i: int): Value {.inline.} = vint(i.int256)
 
 proc vbinary*(b: string): Value =
   Value(kind: VBinary, b: b.mapIt(it.byte))
 
 proc vbinary*(b: seq[byte]): Value =
   Value(kind: VBinary, b: b)
-
-proc `==`*(a: Value, b: Value): bool =
-  if a.kind != b.kind:
-    return false
-  case a.kind:
-  of VInt:
-    a.i == b.i
-  of VBinary:
-    a.b == b.b
diff --git a/tests/README.md b/tests/README.md
index 9105f7de1..c44ec940c 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -1,7 +1,3 @@
 # tests
 
 TODO: more vm tests and fixtures!
-
-```bash
-./tests/test.sh
-```
diff --git a/tests/all_tests.nim b/tests/all_tests.nim
new file mode 100644
index 000000000..fc717e157
--- /dev/null
+++ b/tests/all_tests.nim
@@ -0,0 +1,5 @@
+import  ./test_code_stream,
+        ./test_gas_meter,
+        ./test_memory,
+        ./test_stack
+
diff --git a/tests/build_test.sh b/tests/build_test.sh
deleted file mode 100755
index 1b2731f0d..000000000
--- a/tests/build_test.sh
+++ /dev/null
@@ -1,6 +0,0 @@
-#!/bin/bash
-
-nim cpp tests/code_stream_test.nim
-nim cpp tests/gas_meter_test.nim
-nim cpp tests/memory_test.nim
-nim cpp tests/stack_test.nim
diff --git a/tests/nim.cfg b/tests/nim.cfg
deleted file mode 100644
index 149123bad..000000000
--- a/tests/nim.cfg
+++ /dev/null
@@ -1 +0,0 @@
--p:"../src"
diff --git a/tests/test.sh b/tests/test.sh
deleted file mode 100755
index e52aa9fed..000000000
--- a/tests/test.sh
+++ /dev/null
@@ -1,7 +0,0 @@
-#!/bin/bash
-
-./tests/code_stream_test
-./tests/gas_meter_test
-./tests/memory_test
-./tests/stack_test
-
diff --git a/tests/code_stream_test.nim b/tests/test_code_stream.nim
similarity index 97%
rename from tests/code_stream_test.nim
rename to tests/test_code_stream.nim
index 613cfc9a3..972ac90d6 100644
--- a/tests/code_stream_test.nim
+++ b/tests/test_code_stream.nim
@@ -1,4 +1,5 @@
-import unittest, strutils, sequtils, opcode_values, vm / code_stream
+import  unittest, strutils, sequtils,
+        ../src/opcode_values, ../src/vm/code_stream
 
 suite "parse bytecode":
   test "accepts bytes":
diff --git a/tests/gas_meter_test.nim b/tests/test_gas_meter.nim
similarity index 94%
rename from tests/gas_meter_test.nim
rename to tests/test_gas_meter.nim
index 23061cd39..d43b7f13f 100644
--- a/tests/gas_meter_test.nim
+++ b/tests/test_gas_meter.nim
@@ -1,4 +1,6 @@
-import unittest, macros, strformat, strutils, sequtils, constants, opcode_values, errors, logging, vm / gas_meter, ttmath
+import  unittest, macros, strformat, strutils, sequtils,
+        ttmath,
+        ../src/[constants, opcode_values, errors, logging, vm/gas_meter]
 
 # TODO: quicktest
 # PS: parametrize can be easily immitated, but still quicktests would be even more useful
@@ -63,7 +65,7 @@ suite "gasMeter":
   #     expect(ValidationError):
   #       gasMeter.returnGas(-1.i256)
 
-  # TODO: -0/+0 
+  # TODO: -0/+0
   test "consume spends":
     all(gasMeter):
       check(gasMeter.gasRemaining == gasMeter.startGas)
diff --git a/tests/memory_test.nim b/tests/test_memory.nim
similarity index 94%
rename from tests/memory_test.nim
rename to tests/test_memory.nim
index e9ac1fc0e..0e2a87bbb 100644
--- a/tests/memory_test.nim
+++ b/tests/test_memory.nim
@@ -1,4 +1,6 @@
-import unittest, macros, strformat, strutils, sequtils, constants, opcode_values, errors, vm / memory, ttmath
+import  unittest, macros, strformat, strutils, sequtils,
+        ttmath,
+        ../src/[constants, opcode_values, errors, vm/memory]
 
 proc memory32: Memory =
   result = newMemory()
@@ -27,7 +29,7 @@ suite "memory":
 
   test "write rejects invalid size":
     # expect(ValidationError):
-    #   var mem = memory32()  
+    #   var mem = memory32()
     #   mem.write(startPosition = 0.i256, size = -1.i256, value = @[1.byte, 0.byte])
     expect(ValidationError):
       var mem = memory32()
@@ -37,7 +39,7 @@ suite "memory":
     expect(ValidationError):
       var mem = memory32()
       mem.write(startPosition = 0.u256, size = 4.u256, value = @[1.byte, 0.byte])
-  
+
   test "write rejects valyes beyond memory size":
     expect(ValidationError):
       var mem = memory128()
diff --git a/tests/opcode_test.nim b/tests/test_opcode.nim
similarity index 100%
rename from tests/opcode_test.nim
rename to tests/test_opcode.nim
diff --git a/tests/stack_test.nim b/tests/test_stack.nim
similarity index 92%
rename from tests/stack_test.nim
rename to tests/test_stack.nim
index 937a7b0e5..1d0b716ea 100644
--- a/tests/stack_test.nim
+++ b/tests/test_stack.nim
@@ -1,4 +1,7 @@
-import unittest, macros, strformat, strutils, sequtils, constants, opcode_values, errors, vm / [stack, value], ttmath, utils / [bytes, padding], utils_numeric
+import  unittest, macros, strformat, strutils, sequtils,
+        ttmath,
+        ../src/[constants, opcode_values, errors, utils_numeric, vm/stack, vm/value, utils/bytes, utils/padding]
+
 
 template testPush(value: untyped, expected: untyped): untyped =
   var stack = newStack()
@@ -17,7 +20,7 @@ suite "stack":
     testPush("ves".toBytes, "ves".toBytes.bigEndianToInt)
 
     testFailPush("yzyzyzyzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz".toBytes)
-    
+
   test "push does not allow stack to exceed 1024":
     var stack = newStack()
     for z in 0 .. < 1024:
@@ -37,7 +40,7 @@ suite "stack":
     check(stack.len == 1024)
     expect(FullStack):
       stack.dup(1)
-  
+
   test "pop returns latest stack item":
     var stack = newStack()
     for element in @[1'u, 2'u, 3'u]:
@@ -78,7 +81,7 @@ suite "stack":
     var stack = newStack()
     expect(InsufficientStack):
       stack.swap(0)
-  
+
   test "dup raises InsufficientStack appropriately":
     var stack = newStack()
     expect(InsufficientStack):
diff --git a/tests/vm_test.nim b/tests/test_vm.nim
similarity index 100%
rename from tests/vm_test.nim
rename to tests/test_vm.nim
diff --git a/tests/vm_json_test.nim b/tests/test_vm_json.nim
similarity index 100%
rename from tests/vm_json_test.nim
rename to tests/test_vm_json.nim