try something completely different

.circleci/config.yml

-# Modeled on https://circleci.com/docs/2.0/language-haskell/
+# Copyright 2019 PrivateStorage.io, LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 version: 2.1
+
 jobs:
-  build:
+  test:
     docker:
-      - image: "fpco/stack-build:lts"
+      - image: "nixos/nix:2.2.1"
     steps:
-      - "checkout"
-      - restore_cache:
-          # Read about caching dependencies: https://circleci.com/docs/2.0/caching/
-          name: "Restore Cached Dependencies"
-          keys:
-            - paymentserver-haskell-v1-{{ checksum "stack.yaml" }}-{{ checksum "PaymentServer.cabal" }}
-            - paymentserver-haskell-v1-{{ checksum "stack.yaml" }}
-      - run:
-          name: "Resolve/Update Dependencies"
-          command: "stack --no-terminal setup"
       - run:
-          name: "Run tests"
-          command: "stack --no-terminal test --coverage"
+          name: "Install Git"
+          command: |
+            # Required for the checkout and run steps
+            nix-env -i git openssh
+
+      - "checkout"
+
       - run:
-          name: "Install executable"
-          command: "stack --no-terminal install"
-      - save_cache:
-          name: "Cache Dependencies"
-          key: cci-demo-haskell-v1-{{ checksum "stack.yaml" }}-{{ checksum "PaymentServer.cabal" }}
-          paths:
-            - "/root/.stack"
-            - ".stack-work"
-      - store_artifacts:
-          # Upload executable
-          path: "~/.local/bin/PaymentServer-exe"
-          destination: "PaymentServer-exe"
+          name: "Run Tests"
+          command: |
+            stack test --coverage
+
+workflows:
+  version: 2
+  everything:
+    jobs:
+      - "test"