• mount with noatime, disable hibernation, use a ramdisk: instructions
• Disable sudden motion sensor: instructions
• System Preferences > Energy Saver > Uncheck “Put the hard disk to sleep when possible”

Mounting with noatime can speed up unit tests on conventional spinning disks, too. Be careful if you use something like tmpreaper or mutt, since these rely on up-to-date atimes.

Update: I didn’t see any improvement on our large test suite. Results before and after were basically identical. I ran the suite 3 times and I rebooted between each group of tests.

To disable atime updates, put this in /System/Library/LaunchDaemons/com.nullvision.noatime.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" 
        "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
    <dict>
        <key>Label</key>
        <string>com.nullvision.noatime</string>
        <key>ProgramArguments</key>
        <array>
            <string>mount</string>
            <string>-vuwo</string>
            <string>noatime</string>
            <string>/</string>
        </array>
        <key>RunAtLoad</key>
        <true/>
    </dict>
</plist>

via: nullVision