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https://github.com/GoogleContainerTools/container-structure-test

validate the structure of your container images
https://github.com/GoogleContainerTools/container-structure-test

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validate the structure of your container images

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README 

        
Container Structure Tests

====================



The Container Structure Tests provide a powerful framework to validate the structure

of a container image. These tests can be used to check the output of commands

in an image, as well as verify metadata and contents of the filesystem.



Tests can be run either through a standalone binary, or through a Docker image.



**Note: container-structure-test is not an officially supported Google project, and is currently in maintainence mode. Contributions are still welcome!**



## Installation



### OS X



Install via [brew](https://brew.sh/):



```bash

$ brew install container-structure-test

```



```shell

curl -LO https://github.com/GoogleContainerTools/container-structure-test/releases/latest/download/container-structure-test-darwin-arm64 && chmod +x container-structure-test-darwin-amd64 && sudo mv container-structure-test-darwin-amd64 /usr/local/bin/container-structure-test

```



### Linux

```shell

curl -LO https://github.com/GoogleContainerTools/container-structure-test/releases/latest/download/container-structure-test-linux-amd64 && chmod +x container-structure-test-linux-amd64 && sudo mv container-structure-test-linux-amd64 /usr/local/bin/container-structure-test

```



If you want to avoid using sudo:



```shell

curl -LO https://github.com/GoogleContainerTools/container-structure-test/releases/latest/download/container-structure-test-linux-amd64 && chmod +x container-structure-test-linux-amd64 && mkdir -p $HOME/bin && export PATH=$PATH:$HOME/bin && mv container-structure-test-linux-amd64 $HOME/bin/container-structure-test

```



> [!warning]

> Container builds are currently not updated with new releases



Additionally, a container image for running tests through Google Cloud Builder can be found

at `gcr.io/gcp-runtimes/container-structure-test:latest`.



## Setup

To use container structure tests to validate your containers, you'll need the following:

- The container structure test binary or docker image

- A container image to test against

- A test `.yaml` or `.json` file with user defined structure tests to run inside of the specified container image



Note that the test framework looks for the provided image in the local Docker

daemon (if it is not provided as a tar). The `--pull` flag can optionally

be provided to force a pull of a remote image before running the tests.



## Example Run

An example run of the test framework:

```shell

container-structure-test test --image gcr.io/registry/image:latest \

--config config.yaml

```



Tests within this framework are specified through a YAML or JSON config file,

which is provided to the test driver via a CLI flag. Multiple config files may

be specified in a single test run. The config file will be loaded in by the

test driver, which will execute the tests in order. Within this config file,

four types of tests can be written:



- Command Tests (testing output/error of a specific command issued)

- File Existence Tests (making sure a file is, or isn't, present in the

file system of the image)

- File Content Tests (making sure files in the file system of the image

contain, or do not contain, specific contents)

- Metadata Test, *singular* (making sure certain container metadata is correct)



## Command Tests

Command tests ensure that certain commands run properly in the target image.

Regexes can be used to check for expected or excluded strings in both `stdout`

and `stderr`. Additionally, any number of flags can be passed to the argument

as normal. Each command in the setup section will run in a separate container

and then commits a modified image to be the new base image for the test run.



#### Supported Fields:



**NOTE: `schemaVersion` must be specified in all container-structure-test yamls. The current version is `2.0.0`.**



- Name (`string`, **required**): The name of the test

- Setup (`[][]string`, *optional*): A list of commands

(each with optional flags) to run before the actual command under test.

- Teardown (`[][]string`, *optional*): A list of commands

(each with optional flags) to run after the actual command under test.

- Command (`string`, **required**): The command to run in the test.

- Args (`[]string`, *optional*): The arguments to pass to the command.

- EnvVars (`[]EnvVar`, *optional*): A list of environment variables to set for

the individual test. See the **Environment Variables** section for more info.

- Expected Output (`[]string`, *optional*): List of regexes that should

match the stdout from running the command.

- Excluded Output (`[]string`, *optional*): List of regexes that should **not**

match the stdout from running the command.

- Expected Error (`[]string`, *optional*): List of regexes that should

match the stderr from running the command.

- Excluded Error (`[]string`, *optional*): List of regexes that should **not**

match the stderr from running the command.

- Exit Code (`int`, *optional*): Exit code that the command should exit with.



Example:

```yaml

commandTests:

  - name: "gunicorn flask"

    setup: [["virtualenv", "/env"], ["pip", "install", "gunicorn", "flask"]]

    command: "which"

    args: ["gunicorn"]

    expectedOutput: ["/env/bin/gunicorn"]

  - name:  "apt-get upgrade"

    command: "apt-get"

    args: ["-qqs", "upgrade"]

    excludedOutput: [".*Inst.*Security.* | .*Security.*Inst.*"]

    excludedError: [".*Inst.*Security.* | .*Security.*Inst.*"]

```



Depending on your command the argument section can get quite long. Thus, you

can make use of YAML's list style option for separation of arguments and the

literal style option to preserve newlines like so:



```shell

commandTests:

  - name: "say hello world"

    command: "bash"

    args:

      - -c

      - |

         echo hello &&

         echo world

```



### Image Entrypoint



To avoid unexpected behavior and output when running commands in the

containers, **all entrypoints are overwritten by default.** If your

entrypoint is necessary for the structure of your container, use the

`setup` field to call any scripts or commands manually before running

the tests.



```yaml

commandTests:

  ...

  setup: [["my_image_entrypoint.sh"]]

  ...

```



### Intermediate Artifacts

Each command test run creates either a container (with the `docker` driver) or

tar artifact (with the `tar` driver). By default, these are deleted after the

test run finishes, but the `--save` flag can optionally be passed to keep

these around. This would normally be used for debugging purposes.



## File Existence Tests

File existence tests check to make sure a specific file (or directory) exist

within the file system of the image. No contents of the files or directories

are checked. These tests can also be used to ensure a file or directory is

**not** present in the file system.



#### Supported Fields:



- Name (`string`, **required**): The name of the test

- Path (`string`, **required**): Path to the file or directory under test

- ShouldExist (`boolean`, **required**): Whether or not the specified file or

directory should exist in the file system

- Permissions (`string`, *optional*): The expected Unix permission string (e.g.

  drwxrwxrwx) of the files or directory.

- Uid (`int`, *optional*): The expected Unix user ID of the owner of the file

  or directory.

- Gid (`int`, *optional*): The expected Unix group ID of the owner of the file or directory.

- IsExecutableBy (`string`, *optional*): Checks if file is executable by a given user.

  One of `owner`, `group`, `other` or `any`



Example:

```yaml

fileExistenceTests:

- name: 'Root'

  path: '/'

  shouldExist: true

  permissions: '-rw-r--r--'

  uid: 1000

  gid: 1000

  isExecutableBy: 'group'

```



## File Content Tests

File content tests open a file on the file system and check its contents.

These tests assume the specified file **is a file**, and that it **exists**

(if unsure about either or these criteria, see the above

**File Existence Tests** section). Regexes can again be used to check for

expected or excluded content in the specified file.



#### Supported Fields:



- Name (`string`, **required**): The name of the test

- Path (`string`, **required**): Path to the file under test

- ExpectedContents (`string[]`, *optional*): List of regexes that

should match the contents of the file

- ExcludedContents (`string[]`, *optional*): List of regexes that

should **not** match the contents of the file



Example:

```yaml

fileContentTests:

- name: 'Debian Sources'

  path: '/etc/apt/sources.list'

  expectedContents: ['.*httpredir\.debian\.org.*']

  excludedContents: ['.*gce_debian_mirror.*']

```



## Metadata Test

The Metadata test ensures the container is configured correctly. All

of these checks are optional.



#### Supported Fields:



- EnvVars (`[]EnvVar`): A list of environment variable key/value pairs that should be set

in the container. isRegex (*optional*) interpretes the value as regex.

- UnboundEnvVars (`[]EnvVar`): A list of environment variable keys that should **NOT** be set

in the container.

- Labels (`[]Label`): A list of image labels key/value pairs that should be set on the

container. isRegex (*optional*) interpretes the value as regex.

- Entrypoint (`[]string`): The entrypoint of the container.

- Cmd (`[]string`): The CMD specified in the container.

- Exposed Ports (`[]string`): The ports exposed in the container.

- Unexposed Ports (`[]string`): The ports **NOT** exposed in the container.

- Volumes (`[]string`): The volumes exposed in the container.

- UnmountedVolumes (`[]string`): The volumes **NOT** exposed in the container.

- Workdir (`string`): The default working directory of the container.

- User (`user`): The default user of the container.



Example:

```yaml

metadataTest:

  envVars:

    - key: foo

      value: baz

  labels:

    - key: 'com.example.vendor'

      value: 'ACME Incorporated'

    - key: 'build-date'

      value: '^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{6}$'

      isRegex: true

  exposedPorts: ["8080", "2345"]

  volumes: ["/test"]

  entrypoint: []

  cmd: ["/bin/bash"]

  workdir: "/app"

  user: "luke"

```



## License Tests

License tests check a list of copyright files and makes sure all licenses are

allowed at Google. By default it will look at where Debian lists all copyright

files, but can also look at an arbitrary list of files.



#### Supported Fields:



- Debian (`bool`, **required**): If the image is based on Debian, check where

  Debian lists all licenses.

- Files (`string[]`, *optional*): A list of other files to check.



Example:

```yaml

licenseTests:

- debian: true

  files: ["/foo/bar", "/baz/bat"]

```



### Environment Variables

A list of environment variables can optionally be specified as part of the

test setup. They can either be set up globally (for all test runs), or

test-local as part of individual command test runs (see the **Command Tests**

section above). Each environment variable is specified as a key-value pair.

Unix-style environment variable substitution is supported.



To specify, add a section like this to your config:



```yaml

globalEnvVars:

  - key: "VIRTUAL_ENV"

    value: "/env"

  - key: "PATH"

    value: "/env/bin:$PATH"

```



### Additional Options

The following fields are used to control various options and flags that may be

desirable to set for the running container used to perform a structure test 

against an image. This allows an image author to validate certain runtime

behavior that cannot be modified in the image-under-test such as running a 

container with an alternative user/UID or mounting a volume.



Note that these options are currently only supported with the `docker` driver.



The following list of options are currently supported:

```yaml

containerRunOptions:

  user: "root"                  # set the --user/-u flag

  privileged: true              # set the --privileged flag (default: false)

  allocateTty: true             # set the --tty flag (default: false)

  envFile: path/to/.env         # load environment variables from file and pass to container (equivalent to --env-file)

  envVars:                      # if not empty, read each envVar from the environment and pass to test (equivalent to --env/e)

    - SECRET_KEY_FOO

    - OTHER_SECRET_BAR

  capabilities:                 # Add list of Linux capabilities (--cap-add)

    - NET_BIND_SERVICE

  bindMounts:                   # Bind mount a volume (--volume, -v)

    - /etc/example/dir:/etc/dir

```



## Running Tests On [Google Cloud Build](https://cloud.google.com/cloud-build/docs/)



This tool is released as a builder image, tagged as

`gcr.io/gcp-runtimes/container-structure-test`, so you can specify tests in your

`cloudbuild.yaml`:



```yaml



steps:

# Build an image.

- name: 'gcr.io/cloud-builders/docker'

  args: ['build', '-t', 'gcr.io/$PROJECT_ID/image', '.']

# Test the image.

- name: 'gcr.io/gcp-runtimes/container-structure-test'

  args: ['test', '--image', 'gcr.io/$PROJECT_ID/image', '--config', 'test_config.yaml']



# Push the image.

images: ['gcr.io/$PROJECT_ID/image']

```



## Running File Tests Without Docker



Container images can be represented in multiple formats, and the Docker image

is just one of them. At their core, images are just a series of layers, each

of which is a tarball, and so can be interacted with without a working Docker

daemon. While running command tests currently requires a functioning Docker

daemon on the host machine, File Existence/Content tests do not. This can be

useful when dealing with images which have been `docker export`ed

or saved in a different image format than the Docker format, or when you're simply

trying to run structure tests in an environment where Docker can't be installed.



To run tests without using a Docker daemon, users can specify a different

"driver" to use in the tests, with the `--driver` flag.



An example test run with a different driver looks like:

```shell

container-structure-test test --driver tar --image gcr.io/registry/image:latest \

--config config.yaml

```



The currently supported drivers in the framework are:

- `docker`: the default driver.

Supports all tests, and uses the Docker daemon on the host to run them. You can

set the runtime to use (by example `runsc` to run with gVisor) using `--runtime`

flag.

- `tar`: a tar driver, which extracts an image filesystem to wherever tests are

running, and runs file/metadata tests against it.

Does *not* support command tests.



### Running Structure Tests Through Bazel

Structure tests can also be run through `bazel`.



With Bazel 6 and bzlmod, just see https://registry.bazel.build/modules/container_structure_test.

Otherwise, load the rule and its dependencies in your `WORKSPACE`, see bazel/test/WORKSPACE.bazel in this repo.



Load the rule definition in your BUILD file and declare a `container_structure_test` target, passing in your image and config file as parameters:



```bazel

load("@container_structure_test//:defs.bzl", "container_structure_test")



container_structure_test(

    name = "hello_test",

    configs = ["testdata/hello.yaml"],

    image = ":hello",

)

```



### Flags:

`container-structure-test test -h`

```

  -c, --config stringArray             test config files

      --default-image-tag string       default image tag to used when loading images to the daemon. required when --image-from-oci-layout refers to a oci layout lacking the reference annotation.

  -d, --driver string                  driver to use when running tests (default "docker")

  -f, --force                          force run of host driver (without user prompt)

  -h, --help                           help for test

  -i, --image string                   path to test image

      --image-from-oci-layout string   path to the oci layout to test against

      --metadata string                path to image metadata file

      --no-color                       no color in the output

  -o, --output string                  output format for the test report (available format: text, json, junit) (default "text")

      --platform string                Set platform if host is multi-platform capable (default "linux/amd64")

      --pull                           force a pull of the image before running tests

  -q, --quiet                          flag to suppress output

      --runtime string                 runtime to use with docker driver

      --save                           preserve created containers after test run

      --test-report string             generate test report and write it to specified file (supported format: json, junit; default: json)

 ```

See this [example repo](https://github.com/nkubala/structure-test-examples) for a full working example.



## Output formats



Reports are generated using one of the following output formats: `text`, `json` or `junit`.

Formats like `json` and `junit` can also be used to write a report to a specified file using the `--test-report`.



### Output samples



#### Text



```text

====================================

====== Test file: config.yaml ======

====================================

=== RUN: File Existence Test: whoami

--- PASS

duration: 0s

=== RUN: Metadata Test

--- PASS

duration: 0s



=====================================

============== RESULTS ==============

=====================================

Passes:      2

Failures:    0

Duration:    0s

Total tests: 2



PASS

```



#### JSON



The following sample has been formatted.



```json

{

  "Pass": 2,

  "Fail": 0,

  "Total": 2,

  "Duration": 0,

  "Results": [

    {

      "Name": "File Existence Test: whoami",

      "Pass": true,

      "Duration": 0

    },

    {

      "Name": "Metadata Test",

      "Pass": true,

      "Duration": 0

    }

  ]

}

```



### JUnit



The following sample has been formatted.



```xml



  

    

    

  



```