fix: make Docker tests fail properly (#42)

fix: make tests fail properly

* terminate run-tests.ps1 on the first error;
* split restore and test commands in Dockerfile.

test/Dockerfile

@@ -2,7 +2,7 @@
 # Dockerfile to test the library with multiple versions of PowerShell >= 7.
 #
 # Example run (from repo root):
-# PS > $version="7.1.5"; docker build -f .\test\docker\Dockerfile . -t powershell-featureflags-test:$version --build-arg VERSION=$version --build-arg UBUNTU_VERSION=18.04 && docker run powershell-featureflags-test:$version
+# PS > $version="7.1.5"; docker build -f .\test\Dockerfile . -t powershell-featureflags-test:$version --build-arg VERSION=$version --build-arg UBUNTU_VERSION=18.04 && docker run powershell-featureflags-test:$version
 
 ARG VERSION=7.2.5
 ARG UBUNTU_VERSION=16.04
@@ -26,6 +26,9 @@ RUN ln -s /usr/share/dotnet/dotnet /usr/bin/dotnet
 # Copy the application code.
 WORKDIR /app
 COPY . .
+# Restore dependencies.
+RUN pwsh tools/restore.ps1
+
+# Run tests.
+CMD ["pwsh", "tools/run-tests.ps1"]
 
-# Restore dependencies and run tests.
-CMD pwsh tools/restore.ps1; pwsh tools/run-tests.ps1

tools/run-tests.ps1

@@ -1,3 +1,6 @@
+# Fail on the first error.
+$ErrorActionPreference = "Stop"
+
 $parentDir = Split-Path -Parent (Split-Path -Parent $PSCommandPath)
 $testDir = Join-Path $parentDir -ChildPath "test"