create a totally separate elm project for elm/core tests

elm/core is special because the compiler always inserts an implicit
dependency on it.  therefore it's impossible to have the tests
integrated in the elm/core project in the normal way -- if we try to
symlink out from $ELM_HOME to our project's source in the way that was
done for 0.18, the compiler gets into a deadlock.  other approaches
cause it to find two copies of all the code in elm/core and refuse to
proceed.

instead, this approach creates a logically independent project, with
no real code, only tests.

.gitignore

@@ -1,3 +1,7 @@
 elm-stuff
 tests/test.js
-node_modules/
+node_modules/
+*.dat
+doc*.json
+tests/.elm
+*~

tests/elm.json

@@ -0,0 +1,28 @@
+{
+    "type": "application",
+    "source-directories": [
+        "src"
+    ],
+    "elm-version": "0.19.0",
+    "dependencies": {
+        "direct": {
+            "elm/browser": "1.0.1",
+            "elm/core": "1.0.2",
+            "elm/html": "1.0.0"
+        },
+        "indirect": {
+            "elm/json": "1.1.2",
+            "elm/time": "1.0.0",
+            "elm/url": "1.0.0",
+            "elm/virtual-dom": "1.0.2"
+        }
+    },
+    "test-dependencies": {
+        "direct": {
+            "elm-explorations/test": "1.2.1"
+        },
+        "indirect": {
+            "elm/random": "1.0.0"
+        }
+    }
+}

tests/run-tests.sh

@@ -1,19 +1,70 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
-cd "$(dirname "$0")"
-set -e
+set -o errexit;
+set -o nounset;
 
+#let the caller supply an ELM_TEST binary if desired
+if [ ! -v ELM_TEST ]; then
+    npm install elm-test;
+    ELM_TEST=node_modules/elm-test/bin/elm-test;
+fi
 
-elm-package install -y
+# since elm/core is treated specially by the compiler (it's always
+# inserted as a dependency even when not declared explicitly), we use
+# a bit of a hack to make the tests run against the local source code
+# rather than the elm/core source fetched from package.elm-lang.org.
 
-VERSION_DIR="$(ls elm-stuff/packages/elm-lang/core/)"
-CORE_PACKAGE_DIR="elm-stuff/packages/elm-lang/core/$VERSION_DIR"
+# create a local directory where the compiler will look for the
+# elm/core source code:
+
+DIR="$(dirname $0)";
+
+cd "$DIR";
+
+export ELM_HOME="$(pwd)/.elm";
+
+rm -rf "$ELM_HOME" && mkdir -p "$ELM_HOME";
+
+# elm-test also puts some things in elm-stuff, start with a clean
+# slate there as well
+
+rm -rf elm-stuff;
+
+# now make an initial run of the tests to populate .elm and elm-stuff;
+# this will test against elm/core from package.elm-lang.org, so we
+# don't really care what the results are; we just need to force all
+# the *other* dependencies to be fetched and set up.
+
+echo "seeding framework for test dependencies ...";
+
+# '|| true' lets us ignore failures here and keep the script running.
+# useful when developing a fix for a bug that exists in the version of
+# elm/core hosted on package.elm-lang.org
+"${ELM_TEST}" tests/Main.elm > /dev/null || true;
+
+# clear out the copy of elm-core fetched by the above and replace it
+# with the local source code we want to actually test
+
+VERSION_DIR="$(ls ${ELM_HOME}/0.19.0/package/elm/core/)"
+CORE_PACKAGE_DIR="${ELM_HOME}/0.19.0/package/elm/core/$VERSION_DIR"
 CORE_GIT_DIR="$(dirname $PWD)"
 
+echo; 
 echo "Linking $CORE_PACKAGE_DIR to $CORE_GIT_DIR"
-rm -rf $CORE_PACKAGE_DIR
-ln -s $CORE_GIT_DIR $CORE_PACKAGE_DIR
+echo; 
+rm -rf "$CORE_PACKAGE_DIR"
+ln -sv "$CORE_GIT_DIR" "$CORE_PACKAGE_DIR"
+rm -vf "${CORE_GIT_DIR}"/*.dat "${CORE_GIT_DIR}"/doc*.json
+
+# we also need to clear out elm-test's elm-stuff dir, since otherwise
+# the compiler complains that its .dat files are out of sync
+
+rm -rf elm-stuff;
+
+# now we can run the tests against the symlinked source code for real
 
-elm-make --yes --output test.js Main.elm
+echo;
+echo "running tests ...";
+echo;
 
-elm-test Main.elm
+"${ELM_TEST}" tests/Main.elm;