See Rails parallel test speed with various cores

speedrun.sh

#!/bin/bash

# Get the number of CPU cores available
num_cores=$(nproc)

# Set the test seed to ensure the tests are deterministic
seed=$(ruby -e 'puts Random.new_seed')

# Create a temporary file to store the results
output_file="test_times.txt"

# Print table headers
echo -e "Cores\tTime (seconds)" > $output_file

# Loop through core counts from 1 to the number of cores
for (( cores=1; cores<=$num_cores; cores++ ))
do
  echo "Running tests with $cores core(s)..."

  # Run the tests with the specified number of cores and capture the time
  start_time=$(date +%s)

  PARALLEL_WORKERS=$cores SEED=$seed rails test

  end_time=$(date +%s)
  elapsed_time=$((end_time - start_time))

  # Output the result in the table format
  echo -e "$cores\t$elapsed_time" >> $output_file
done

# Display the results
echo "Test results saved to $output_file"
cat $output_file