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Build and Test

This guide gets you started with building and testing Snap. If you have commits you want to contribute, review the CONTRIBUTING file for a shorter list of what we look for and come back here if you need to verify your environment is configured correctly and you have the right type of tests.

Getting Started

If you prefer a video walkthrough of this process, watch this tutorial.

To build the Snap framework you'll need:

The instructions below assume that the GOPATH environment variable has been set properly. Many of us use go version manager (gvm) to easily switch between Go versions.

Now you can download Snap into your $GOPATH:

$ # -d is used to download Snap without building it
$ go get -d
$ cd $GOPATH/src/

In the snap/ directory there's a Makefile that builds all dependencies and then the Snap Framework binaries. To get dependencies and build Snap run:

$ cd $GOPATH/src/
$ make

By default make runs make deps, make snap, and make plugins commands for you. Alternatively, you can run make with any of these other targets:

  • deps: fetches all dependencies using glide
  • test-(legacy|small|medium|large): runs test suite
  • all: builds snapteld, snaptel, and test plugins for all platforms (MacOS and Linux)
  • snap builds snapteld and snaptel for local operating system
  • plugins builds test plugins for local operating system
  • install: installs snapteld and snaptel binaries in /usr/local/bin

To see how to use Snap, look at getting started,, and


Creating Tests

Our tests are written using smartystreets' GoConvey package. See for an introduction to creating a test using this package.

Our process for creating large tests is a little different since the adoption of our large test framework. For specific instructions on large tests, visit

Tests in Go

We follow the Go methodology of placing tests into files with names that look like *_test.go. See this section from go command documentation for more details.

Test Types in Snap

Tests in Snap are broken down into small, medium, and large tests. These three test types can be best described as follows:

  • Small tests are written to exercise behavior within a single function or module. While of you might think of these as unit tests, a more generic term seems appropriate to avoid any confusion. In general, there is no reliance in a small test on any external systems (databases, web servers, etc.), and responses expected from such external services (if any) will be mocked or faked. When we say reliance on “external systems” we are including reliance on access to the network, the filesystem, external systems (eg. databases), system properties, multiple threads of execution, or the use of sleep statements as part of the test. These tests should be the easiest to automate and the fastest to run (returning a result in a minute or less, with most returning a result in a few seconds or less). These tests will be run automatically on any pull requests received from a contributor, and all small tests must pass before a pull request will be reviewed.
  • Medium tests involve two or more features and test the interaction between those features. For those with previous testing experience, you might think of these as integration tests, but because there are a large number of other types of tests that fall into this category a more generic term is needed. The question being answered by these tests is whether or not the interactions between a feature and its nearest neighbors interoperate the way that they are expected to. Medium tests can rely on access to local services (a local database, for example), the local filesystem, multiple threads of execution, sleep statements and even access to the (local) network. However, reliance on access to external systems and services (systems and services not available on the localhost) in medium tests is discouraged. In general, we should expect that these tests return a result in 5 minutes or less, although some medium tests may return a result in much less time than that (depending on local system load). These tests can typically be automated and the set of medium tests will be run against any builds prior to their release.
  • Large tests represent typical user scenarios and might be what some of you would think of as functional tests. However, as was the case with the previous two categories, we felt that the more generic term used by the Google team seemed to be appropriate here. For these tests, reliance on access to the network, local services (like databases), the filesystem, external systems, multiple threads of execution, system properties, and the use of sleep statements within the tests are all supported. Some of these tests might be run manually as part of the release process, but every effort is made to ensure that even these large tests can be automated (where possible). The response times for testing of some of these user scenarios could be 15 minutes or more (eg. it may take some time to bring the system up to an equilibrium state when load testing), so there are situations where these large tests will have to be triggered manually even if the test itself is run as an automated test. More information about Snap's large test framework can be found in

This taxonomy is the same taxonomy used by the Google Test team and was described in a posting to the Google Testing Blog that can be found here.

Tagging Tests in Go

But, how do you actually tag a test as small, medium, or large in Go? As it turns out, this is a relatively simple process. To tag a given test file by the category of tests that it contains, all we have to do is add a single line to the beginning of the file that provides a build tag for that file. For example, a line like this:

// +build small

would identify that file as a file that contains small tests, while a line like this as the first line of the file:

 // +build medium

would identify that file as a file that contains medium tests. Once those build tags have been added to the test files in the Snap codebase, it is relatively simple to run a specific set of tests (by type) by simply adding a -tags [TAG] command-line flag to the go test command (where the [TAG] value is replaced by one of our test types). For example, this command will run all of the tests in the current working directory or any of its subdirectories that have been tagged as small tests:

 $ go test -v  -tags=small ./...

It should be noted here that if there are any untagged tests in the directory referenced by the go test command, those untagged tests will also be run, regardless of the -tags [TAG] option that is passed into the go test command. To deal with this issue, all preexisting tests in the Snap framework have been tagged with a legacy tag. We have also modified the current test matrix (in the appropriate TravisCI and test shell-script files) to run both the small and legacy tests until such time that we feel that there is sufficient test coverage by the small tests that are currently being developed).

Once the maintainers feel that the small tests provide sufficient code coverage, the existing legacy tests will be phased out (or used in the construction of a set of medium and large tests for the Snap CI/CD toolchain). All new tests being added to the Snap framework by contributors should be marked as either small, medium, or large tests, depending on their scope.

Building Effective Tests


Any small tests added to the Snap framework must conform to the following constraints:

  • They should test the behavior of a single function or method in the framework
  • There should no reliance rely on external systems or system-level resources (eg. networks, filesystem, external systems or services, system properties, multiple threads of execution, or the use of sleep statements) as part of these tests; the expected responses of any such external systems or access to system-level resources should be mocked appropriately.
  • They should be independent of any other tests in the test framework
  • They should return the same result every time they are run, regardless of the environment they are run in (a failure of any of these tests should be indicative of an issue with the code being tested, not the environment that the test is being run in)

When complete, the full set of small tests for any given function or method should provide sufficient code coverage to ensure that any changes made to that function or method will not 'break the build'. This will assure the Snap maintainers that any pull requests that are made to modify or add to the framework can be safely merged (provided that there is sufficient code coverage and the associated tests pass).

It should be noted here that the maintainers will refuse to merge any pull requests that trigger a failure of any of the small or legacy tests that cover the code being modified or added to the framework. As such, we highly recommend that contributors run the tests that cover their contributions locally before submitting their contribution as a pull request. Maintainers may also ask that contributors add tests to their pull requests to ensure adequate code coverage before they are willing to accept a given pull request, even if all existing tests pass. Our hope is that you, as a contributor, will understand the need for this requirement.


More information about large tests can be found in

Running Tests

On a local machine

Contributors are assumed to have run the legacy and small tests that cover their contribution on their local machine prior to submitting the corresponding pull request. There are several ways of accomplishing this depending on the coverage required.

Before any tests can be run, the following command should be executed to pull down all of the test dependencies to the local machine (note; this will also run the ./scripts/ script, see below for more details):

$ cd $GOPATH/src/

where the string [SNAP_TEST_TYPE] that is shown above is replaced with one of our test types (legacy, small, medium, or large). Once the dependencies have been pulled down to the local machine, there are a number of ways to run the various tests included in the Snap framework. To run the complete set of legacy, small, medium, or large tests in the Snap framework (and stop at the first failure in a directory before continuing on), you can simply use the same shell-script that is run by the make test command that was shown above:

$ ./scripts/ [SNAP_TEST_TYPE]

As was the case in the make test command that was shown above, the string [SNAP_TEST_TYPE] that is shown in this command should be replaced by the type of tests you wish to run (legacy, small, medium, or large). Note, that for convenience we have also added four new targets to the Snap Makefile that can be used to run the legacy, small, medium, or large tests in a simple make test-* command. To run the small tests, for example, one could simply run a command that looks something like this:

$ make test-small

To run the other types of tests in the Snap framework, simply replace the small type with one of the other types (legacy, medium, or large in the example make test-* command shown above).

If you are interested in running all of the legacy tests from the Snap framework and continuing through to all subdirectories, regardless of any errors that might be encountered, then you can run a go test ... command directly (instead of running a make test-* or scripts/ [SNAP_TEST_TYPE] command like those shown above). That go test ... command would look something like this:

go test -tags=legacy ./...

It should be noted here that the go test ... command shown above will iterate over all of the subdirectories of the current working directory and run all of the legacy tests found. It will not stop if errors are detected during a test run; those errors will simply be reported as part of the output of the go test ... command.

To run all of the small tests from the Snap framework, one would simply change the value of the tag passed into the command from legacy to small:

go test -tags=small ./...

All tests in the Snap framework are tagged as legacy, small, medium, or large, so at least one of those tags must be provided to any go test ... command that is executed by a contributor.

Individual tests from the framework can also be selected and run by passing a test name into the go test... command using the -run command-line flag:

go test -v -tags=legacy -run=[TEST_NAME] ./...

e.g. to run the TestLoad test from control_test.go, one would simply run a command that looks something like this:

go test -v -tags=legacy -run=TestLoad ./...

Finally, coverage reports can be generated that show (on a function-by-function level) how well a given test or set of tests cover the current codebase. For example, the following pair of commands will generate a report showing the coverage of all of the legacy tests in the current working directory (as text output to the console):

go test -tags=small -coverprofile=/tmp/coverage.out . && go tool cover -func=/tmp/coverage.out

A similar pair of commands can be used to generate an HTML view showing the same information, but in a browsable view that shows how the matching tests cover the code on a line-by-line basis for each file in the current working directory (the resulting view will open in the default web browser defined on the local machine)

go test -tags=small -coverprofile=/tmp/coverage.out . && go tool cover -html=/tmp/coverage.out

As was the case with the previous commands, the -run command-line flag can be used to further reduce the scope of the generated report to only show the coverage of named test. It should be noted here that these coverage reports can only be generated for code in a single directory. The -coverprofile command-line flag cannot be used to generate a coverage report across all subdirectories as was shown in the go test ... command shown previously.

In Docker

The Snap Framework supports running tests in an isolated container as opposed to your local host. Run the test script, which calls a Dockerfile located at ./scripts/Dockerfile:

$ cd $GOPATH/src/
$ scripts/ [SNAP_TEST_TYPE]