[test-format] Add base document for general test format

specs/test-format.md

@@ -0,0 +1,71 @@
+# General test format
+
+This document defines the general YAML format to which all tests should conform.
+
+## ToC
+
+* [About](#about)
+* [YAML Fields](#yaml-fields)
+* [Example test suite](#example-test-suite)
+
+## About
+Ethereum 2.0 uses YAML as the format for all cross client tests. This document describes at a high level the general format to which all test files should conform.
+
+The particular formats of specific types of tests (test suites) are defined in separate documents.
+
+## YAML fields
+`title` _(required)_
+
+`summary` _(optional)_
+
+`test_suite` _(required)_ string defining the test suite to which the test cases conform
+
+`fork` _(required)_ production release versioning
+
+`version` _(required)_ version for particular test document
+
+`test_cases` _(required)_ list of test cases each of which is formatted to conform to the `test_case` standard defined by `test_suite`. All test cases have optional `name` and `description` string fields.
+
+## Example test suite
+`shuffle` is a test suite that defines test cases for the `shuffle()` helper function defined in the `beacon-chain` spec.
+
+Test cases that conform to the `shuffle` test suite have the following fields:
+
+* `input` _(required)_ the list of items passed into `shuffle()`
+* `output` _(required)_ the expected list returned by `shuffle()`
+* `seed` _(required)_ the seed of entropy passed into `shuffle()`
+
+As for all test cases, `name` and `description` are optional string fields.
+
+The following is a sample YAML document for the `shuffle` test suite:
+
+```yaml
+title: Shuffling Algorithm Tests
+summary: Test vectors for shuffling a list based upon a seed using `shuffle`
+test_suite: shuffle
+fork: tchaikovsky
+version: 1.0
+
+test_cases:
+- input: []
+  output: []
+  seed: !!binary ""
+- name: boring_list
+  description: List with a single element, 0
+  input: [0]
+  output: [0]
+  seed: !!binary ""
+- input: [255]
+  output: [255]
+  seed: !!binary ""
+- input: [4, 6, 2, 6, 1, 4, 6, 2, 1, 5]
+  output: [1, 6, 4, 1, 6, 6, 2, 2, 4, 5]
+  seed: !!binary ""
+- input: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
+  output: [4, 7, 10, 13, 3, 1, 2, 9, 12, 6, 11, 8, 5]
+  seed: !!binary ""
+- input: [65, 6, 2, 6, 1, 4, 6, 2, 1, 5]
+  output: [6, 65, 2, 5, 4, 2, 6, 6, 1, 1]
+  seed: !!binary |
+    JlAYJ5H2j8g7PLiPHZI/rTS1uAvKiieOrifPN6Moso0=
+```