diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
new file mode 100644
index 0000000..b6603f4
--- /dev/null
+++ b/.github/workflows/ci.yaml
@@ -0,0 +1,28 @@
+name: CI
+
+on: [push, pull_request]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Set up Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.15
+
+      - name: Test
+        run: |
+          ./test.sh
+
+      - name: Run GoReleaser
+        uses: goreleaser/goreleaser-action@v2
+        with:
+          args: build --snapshot
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.gitignore b/.gitignore
index 777d93c..bb434fe 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,5 @@
+# ignore built binaries
 /terraform-demux
+
+# ignore test output
+test-log
diff --git a/test.sh b/test.sh
new file mode 100755
index 0000000..5062e9b
--- /dev/null
+++ b/test.sh
@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+
+set -e
+
+GIT_ROOT="$(git rev-parse --show-toplevel)"
+TMP_DIR="$(mktemp -d)"
+
+if ! [[ $TMP_DIR ]]; then
+    panic "could not create temporary directory"
+else
+    # shellcheck disable=SC2064
+    trap "rm -r $TMP_DIR" EXIT
+
+    export XDG_CACHE_HOME="$TMP_DIR"
+fi
+
+function terraform_demux_version() {
+    go run "$GIT_ROOT/cmd/..." -- -version >test-log 2>&1
+}
+
+function expect_log() {
+    (grep -q "$1" test-log && pass "Found '$1' in test-log") || fail "Expected to find '$1' in test-log"
+}
+
+function pass() {
+    echo "PASS:" "$@" >&2
+}
+
+function fail() {
+    echo "FAIL:" "$@" >&2
+    exit 1
+}
+
+function panic() {
+    echo "PANIC:" "$@" >&2
+    exit 1
+}
+
+function terraform_demux_version_test() {
+    local dir="$1"
+    local expected_version="$2"
+
+    pushd "$dir" >/dev/null
+
+    terraform_demux_version
+
+    (grep -q "$expected_version" test-log && pass "Found '$expected_version' in $dir/test-log") \
+        || fail "Expected to find '$expected_version' in $dir/test-log"
+
+    popd >/dev/null
+}
+
+function test_pre_0.12_exact() {
+    terraform_demux_version_test "testdata/terraform-pre-0.12-exact" "Terraform v0.11.15"
+}
+
+function test_post_0.12_exact() {
+    terraform_demux_version_test "testdata/terraform-post-0.12-exact" "Terraform v1.0.3"
+}
+
+function test_pessimistic_constraint() {
+    terraform_demux_version_test "testdata/terraform-pessimistic" "Terraform v0.14."
+}
+
+test_pre_0.12_exact
+
+test_post_0.12_exact
+
+test_pessimistic_constraint
diff --git a/testdata/terraform-pessimistic/terraform.tf b/testdata/terraform-pessimistic/terraform.tf
new file mode 100644
index 0000000..b3093ec
--- /dev/null
+++ b/testdata/terraform-pessimistic/terraform.tf
@@ -0,0 +1,3 @@
+terraform {
+  required_version = "~> 0.14.0"
+}
diff --git a/testdata/terraform-post-0.12-exact/terraform.tf b/testdata/terraform-post-0.12-exact/terraform.tf
new file mode 100644
index 0000000..7cfd361
--- /dev/null
+++ b/testdata/terraform-post-0.12-exact/terraform.tf
@@ -0,0 +1,3 @@
+terraform {
+  required_version = "1.0.3"
+}
diff --git a/testdata/terraform-pre-0.12-exact/terraform.tf b/testdata/terraform-pre-0.12-exact/terraform.tf
new file mode 100644
index 0000000..1fb51cf
--- /dev/null
+++ b/testdata/terraform-pre-0.12-exact/terraform.tf
@@ -0,0 +1,3 @@
+terraform {
+  required_version = "0.11.15"
+}