Azure pipeline not applying label to Docker build container

As the title says, I am trying to apply a label to my docker container so I can then reference said container in a further step in my pipeline. My end result that I am going for is to be able to copy my test results out of the container and publish and display those results.

azure-pipeline.yml

# Docker
# Build a Docker image
# https://learn.microsoft.com/azure/devops/pipelines/languages/docker

trigger:
- main
- develop

resources:
- repo: self

variables:
  tag: '$(Build.BuildId)'

stages:
- stage: Build
  displayName: Build image
  jobs:
  - job: Build
    displayName: Build
    pool:
      name: default
    steps:
    - task: Docker@2
      displayName: Build an image
      inputs:
        command: build
        arguments: '--build-arg BuildId=$(Build.BuildId)'
        dockerfile: '$(Build.SourcesDirectory)/Dockerfile'
        tags: |
          $(tag)
    - powershell: |
        $id=docker images --filter "label=test=$(Build.BuildId)" -q | Select-Object -First 1
        docker create --name testcontainer $id
        docker cp testcontainer:/testresults ./testresults
        docker rm testcontainer
      displayName: 'Copy test results'
    - task: PublishTestResults@2
      displayName: 'Publish test results'
      inputs:
        testResultsFormat: 'xUnit'
        testResultsFiles: '**/*.trx'
        searchFolder: '$(System.DefaultWorkingDirectory)/testresults'

Dockerfile

#See https://aka.ms/containerfastmode to understand how Visual Studio uses this Dockerfile to build your images for faster debugging.

FROM mcr.microsoft.com/dotnet/aspnet:6.0-bullseye-slim-amd64 AS base
WORKDIR /app
EXPOSE 80

FROM mcr.microsoft.com/dotnet/sdk:6.0-bullseye-slim-amd64 AS build
WORKDIR /src
COPY ["Forecast/Forecast.csproj", "Forecast/"]
WORKDIR "/src/Forecast"
RUN dotnet restore "Forecast.csproj"
COPY Forecast/ .
RUN dotnet build "Forecast.csproj" -c Release -o /app/build

FROM build AS publish
WORKDIR /src
RUN dotnet publish "Forecast/Forecast.csproj" --no-restore -c Release -o /app/publish

FROM build as test
ARG BuildId
LABEL test=${BuildId}
WORKDIR /src
COPY ["ForecastXUnitTest/ForecastXUnitTest.csproj", "ForecastXUnitTest/"]
WORKDIR "/src/ForecastXUnitTest"

RUN dotnet restore "ForecastXUnitTest.csproj"
COPY ForecastXUnitTest/ .
RUN dotnet build "ForecastXUnitTest.csproj" -c Release -o /app
RUN dotnet test -c Release --results-directory /testresults --logger "trx;LogFileName=test_results.trx" "ForecastXUnitTest.csproj"

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "Forecast.dll"]

I can see that the label hasn't been applied upon inspection of the build steps. The powershell step specifically the line docker create --name testcontainer $id the variable $id is empty and is telling me that the label is never applied so I'm not able to go any further.

I figured out what was causing my issue. Docker ends up with cache'd ephemeral container images when building and doing its thing.

With these in place Docker no longer runs those steps so along the way I added in the steps but with what had preceded in builds I wasn't getting anything from subsequent calls.

On top of this I had been referring to a previous image with the directive FROM that was preventing my directory from being found.