Core gdt library and specification

gdt is a testing library that allows test authors to cleanly describe tests in a YAML file. gdt reads YAML files that describe a test's assertions and then builds a set of structures that can be run by either the gdt command-line interface or the standard Go testing go test tool.

gdt test scenario structure

A gdt test scenario (or just "scenario") is simply a YAML file.

All gdt scenarios have the following fields:

• name: (optional) string describing the contents of the test file. If missing or empty, the filename is used as the name
• description: (optional) string with longer description of the test file contents
• defaults: (optional) is a map of default options and configuration values
• fixtures: (optional) list of strings indicating named fixtures that will be started before any of the tests in the file are run
• depends: (optional) list of Dependency objects that describe a program or package that should be available in the host's PATH that the test scenario depends on.
• depends.name: string name of the program or package the test scenario depends on.
• depends.when: (optional) object describing any constraints/conditions that should apply to the evaluation of the dependency.
• depends.when.os: (optional) string operating system. if set, the dependency is only checked for that OS.
• depends.when.version: (optional) string version constraint. if set, the program or package must be available on the host PATH and must satisfy the version constraint.
• skip-if: (optional) list of Spec specializations that will be evaluated before running any test in the scenario. If any of these conditions evaluates successfully, the test scenario will be skipped.
• tests: list of Spec specializations that represent the runnable test units in the test scenario.

The scenario's tests field is the most important and the Spec objects that it contains are the meat of a test scenario.

gdt test spec structure

A spec represents a single action that is taken and zero or more assertions that represent what you expect to see resulting from that action.

gdt plugins each define a specialized subclass of the base Spec that contains fields that are specific to that type of test.

For example, there is an exec plugin that allows you to execute arbitrary commands and assert expected result codes and output. There is an http that allows you to call an HTTP URL and assert that the response looks like what you expect. There is a kube plugin that allows you to interact with a Kubernetes API, etc.

gdt examines the YAML file that defines your test scenario and uses these plugins to parse individual test specs.

All test specs have the following fields:

• name: (optional) string describing the test unit.
• description: (optional) string with longer description of the test unit.
• timeout: (optional) a string duration of time the test unit is expected to complete within.
• retry: (optional) an object containing retry configurationu for the test unit. Some plugins will automatically attempt to retry the test action when an assertion fails. This field allows you to control this retry behaviour for each individual test.
• retry.interval: (optional) a string duration of time that the test plugin will retry the test action in the event assertions fail. The default interval for retries is plugin-dependent.
• retry.attempts: (optional) an integer indicating the number of times that a plugin will retry the test action in the event assertions fail. The default number of attempts for retries is plugin-dependent.
• retry.exponential: (optional) a boolean indicating an exponential backoff should be applied to the retry interval. The default is is plugin-dependent.
• wait (optional) an object containing wait information for the test unit.
• wait.before: a string duration of time that gdt should wait before executing the test unit's action.
• wait.after: a string duration of time that gdt should wait after executing the test unit's action.
• on: (optional) an object describing actions to take upon certain conditions.
• on.fail: (optional) an object describing an action to take when any assertion fails for the test action.
• on.fail.exec: a string with the exact command to execute upon test assertion failure. You may execute more than one command but must include the on.fail.shell field to indicate that the command should be run in a shell.
• on.fail.shell: (optional) a string with the specific shell to use in executing the command to run upon test assertion failure. If empty (the default), no shell is used to execute the command and instead the operating system's exec family of calls is used.

exec test spec structure

The exec plugin's test spec allows test authors to execute arbitrary commands and assert that the command results in an expected result code or output.

In addition to all the base Spec fields listed above, the exec plugin's test spec also contains these fields:

• exec: a string with the exact command to execute. You may execute more than one command but must include the shell field to indicate that the command should be run in a shell. It is best practice, however, to simply use multiple exec specs instead of executing multiple commands in a single shell call.
• shell: (optional) a string with the specific shell to use in executing the command. If empty (the default), no shell is used to execute the command and instead the operating system's exec family of calls is used.
• var-stdout: (optional) a string with the name of a variable to save the contents of the test spec's stdout stream. This named variable can then be referred from subsequent test specs. Note: this is a shortcut for the longer-form var:{VAR_NAME}:from:stdout
• var-stderr: (optional) a string with the name of a variable to save the contents of the test spec's stderr stream. This named variable can then be referred from subsequent test specs. Note: this is a shortcut for the longer-form var:{VAR_NAME}:from:stderr
• var-rc: (optional) a string with the name of a variable to save the contents of the test spec's return/exitcode value. This named variable can then be referred from subsequent test specs. Note: this is a shortcut for the longer-form var:{VAR_NAME}:from:returncode
• var: (optional) an object describing variables that can have values saved and referred to by subsequent test specs. Each key in the var object is the name of the variable to define. The var.from field contains a string describing where the value for the variable should be sourced.
• var.$VARIABLE_NAME.from: (required) a string describing where the variable with name $VARIABLE_NAME should source its value. The strings stdout, stderr and returncode refer to the corresponding stdout, stderr and return/exitcode values. All other string values for var.from indicate the name of the environment variable to read into the named variable.
• assert: (optional) an object describing the conditions that will be asserted about the test action.
• assert.require: (optional) a boolean indicating whether a failed assertion will cause the test scenario's execution to stop. The default behaviour of gdt is to continue execution of subsequent test specs in a test scenario when an assertion fails.
• assert.exit-code: (optional) an integer with the expected exit code from the executed command. The default successful exit code is 0 and therefore you do not need to specify this if you expect a successful exit code.
• assert.out: (optional) a PipeExpect object containing assertions about content in stdout.
• assert.out.is: (optional) a string with the exact contents of stdout you expect to get.
• assert.out.all: (optional) a string or list of strings that all must be present in stdout.
• assert.out.any: (optional) a string or list of strings of which at least one must be present in stdout.
• assert.out.none: (optional) a string or list of strings of which none should be present in stdout.
• assert.err: (optional) a PipeAssertions object containing assertions about content in stderr.
• assert.err.is: (optional) a string with the exact contents of stderr you expect to get.
• assert.err.all: (optional) a string or list of strings that all must be present in stderr.
• assert.err.any: (optional) a string or list of strings of which at least one must be present in stderr.
• assert.err.none: (optional) a string or list of strings of which none should be present in stderr.

Marking a program or package dependency for a test scenario

Often when creating gdt test scenarios, you will want to declare that the scenario requires a particular application be available in the host's PATH.

Use the depends field to tell gdt about these requirements:

name: scenario requiring `myapp` binary be available to execute

depends:
 - name: myapp

tests:
 - name: start-myapp
   exec: myapp start

Running the above test scenario when myapp is not available to execute results in a runtime error:

$ gdt run myapp.yaml
Error: runtime error: dependency not satisfied: myapp

You can specify that a dependency only be applicable on a specific operating system using the depends.when.os field:

name: scenario requiring `myapp` binary be available to execute

depends:
 - name: myapp
   when:
     os: linux

tests:
 - name: start-myapp
   exec: myapp start

Running the above scenario on Linux yields the same runtime error:

$ gdt run myapp.yaml
Error: runtime error: dependency not satisfied: myapp (OS:linux)

However changing the depends.when.os to windows:

name: scenario requiring `myapp` binary be available to execute

depends:
 - name: myapp
   when:
     os: windows

tests:
 - name: start-myapp
   exec: myapp start

Running the scenario will show a different runtime error that is dependent on the operating system:

$ gdt run myapp.yaml
Error: runtime error: exec: "myapp": executable file not found in $PATH

Passing variables to subsequent test specs

A gdt test scenario is comprised of a list of test specs. These test specs are executed in sequential order. If you want to have one test spec be able to use some output or value calculated or asserted in a previous step, you can use the gdt variable system.

Here's an test scenario that shows how to define variables in a test spec and how to use those variables in later test specs.

file: plugin/exec/testdata/var-save-restore.yaml:

name: var-save-restore
description: a scenario that tests variable save/restore across multiple test specs
tests:
  - exec: echo 42
    var-stdout: VAR_STDOUT

  - exec: echo $$VAR_STDOUT
    var-rc: VAR_RC
    assert:
      out:
        is: 42

  - exec: echo $$VAR_RC
    assert:
      out:
        is: 0

  - exec: echo 42
    assert:
      out:
        is: $$VAR_STDOUT

In the first test spec, we specify that we want to store the value of the stdout stream in a variable called VAR_STDOUT:

  - exec: echo 42
    var-stdout: VAR_STDOUT

In the second test spec, we refer to the VAR_STDOUT variable using the double-dollar-sign notation in the exec field and also specify a VAR_RC variable to contain the value of the return/exitcode from the executed statement (echo 42):

  - exec: echo $$VAR_STDOUT
    var-rc: VAR_RC
    assert:
      out:
        is: 42

NOTE: We use the double-dollar-sign notation because by default, gdt replaces all single-dollar-sign notations with environment variables BEFORE executing the test specs in a test scenario. Using the double-dollar-sign notation means that environment variable substitution does not impact the referencing of gdt variables referenced in a test spec.

In the third test spec, we simply echo out the value of that VAR_RC variable and assert that the stdout stream contains the string "0" (since echo 42 returns 0.):

  - exec: echo $$VAR_RC
    assert:
      out:
        is: 0

Finally, in the fourth step, we demonstrate that we can refer to the VAR_STDOUT variable defined in the very first test spec from the assert.out.is field. This shows the flexibility of the gdt variable system. You can define variables using a simple declarative syntax and then refer to the value of those variables using the double-dollar-sign notation in any subsequent test spec.

Timeouts and retrying assertions

When evaluating assertions for a test spec, gdt inspects the test's timeout value to determine how long to retry the get call and recheck the assertions.

If a test's timeout is empty, gdt inspects the scenario's defaults.timeout value. If both of those values are empty, gdt will look for any default timeout value that the plugin uses.

If you're interested in seeing the individual results of gdt's assertion-checks for a single get call, you can use the gdt.WithDebug() function, like this test function demonstrates:

file: testdata/matches.yaml:

name: matches
description: create a deployment and check the matches condition succeeds
fixtures:
  - kind
tests:
  - name: create-deployment
    kube:
      create: testdata/manifests/nginx-deployment.yaml
  - name: deployment-exists
    kube:
      get: deployments/nginx
    assert:
      matches:
        spec:
          replicas: 2
          template:
            metadata:
              labels:
                app: nginx
        status:
          readyReplicas: 2
  - name: delete-deployment
    kube:
      delete: deployments/nginx

file: matches_test.go

import (
    "github.com/gdt-dev/core"
    _ "github.com/gdt-dev/kube"
    kindfix "github.com/gdt-dev/kube/fixture/kind"
)

func TestMatches(t *testing.T) {
	fp := filepath.Join("testdata", "matches.yaml")

	kfix := kindfix.New()

	s, err := gdt.From(fp)

	ctx := gdt.NewContext(gdt.WithDebug())
	ctx = gdt.RegisterFixture(ctx, "kind", kfix)
	s.Run(ctx, t)
}

Here's what running go test -v matches_test.go would look like:

$ go test -v matches_test.go
=== RUN   TestMatches
=== RUN   TestMatches/matches
=== RUN   TestMatches/matches/create-deployment
=== RUN   TestMatches/matches/deployment-exists
deployment-exists (try 1 after 1.303µs) ok: false, terminal: false
deployment-exists (try 1 after 1.303µs) failure: assertion failed: match field not equal: $.status.readyReplicas not present in subject
deployment-exists (try 2 after 595.62786ms) ok: false, terminal: false
deployment-exists (try 2 after 595.62786ms) failure: assertion failed: match field not equal: $.status.readyReplicas not present in subject
deployment-exists (try 3 after 1.020003807s) ok: false, terminal: false
deployment-exists (try 3 after 1.020003807s) failure: assertion failed: match field not equal: $.status.readyReplicas not present in subject
deployment-exists (try 4 after 1.760006109s) ok: false, terminal: false
deployment-exists (try 4 after 1.760006109s) failure: assertion failed: match field not equal: $.status.readyReplicas had different values. expected 2 but found 1
deployment-exists (try 5 after 2.772416449s) ok: true, terminal: false
=== RUN   TestMatches/matches/delete-deployment
--- PASS: TestMatches (3.32s)
    --- PASS: TestMatches/matches (3.30s)
        --- PASS: TestMatches/matches/create-deployment (0.01s)
        --- PASS: TestMatches/matches/deployment-exists (2.78s)
        --- PASS: TestMatches/matches/delete-deployment (0.02s)
PASS
ok  	command-line-arguments	3.683s

You can see from the debug output above that gdt created the Deployment and then did a kube.get for the deployments/nginx Deployment. Initially (attempt 1), the assert.matches assertion failed because the status.readyReplicas field was not present in the returned resource. gdt retried the kube.get call 4 more times (attempts 2-5), with attempts 2 and 3 failed the existence check for the status.readyReplicas field and attempt 4 failing the value check for the status.readyReplicas field being 1 instead of the expected 2. Finally, when the Deployment was completely rolled out, attempt 5 succeeded in all the assert.matches assertions.

Contributing and acknowledgements

gdt was inspired by Gabbi, the excellent Python declarative testing framework. gdt tries to bring the same clear, concise test definitions to the world of Go functional testing.

The Go gopher logo, from which gdt's logo was derived, was created by Renee French.

Contributions to gdt are welcomed! Feel free to open a Github issue or submit a pull request.