chore(docs/decisions-log.md): add a decision regarding flaky tests

[skip ci]

Author: php-coder

docs/decisions-log.md

@@ -20,6 +20,7 @@
 | 30.12.2017 Workaround | [php-coder/mystamps#772](https://github.com/php-coder/mystamps/issues/772) Because **Travis CI** has **MySQL** version 5.6.43, we can't have a unique index on a column that has a length that exceeds 767 bytes. Our production server is running on 5.7.20 that doesn't have such limitation. In order to be able to run migrations on all the environments, I set type of the `series_import_requests.url` column to `VARCHAR(767)` (instead of `VARCHAR(768)` or `VARCHAR(1024)` as I wanted before). Commits: [33dd9025](https://github.com/php-coder/mystamps/commit/33dd902500501d3fdc3a744229ad921982adbc01) |
 | 20.07.2017 Decision | [php-coder/mystamps#423](https://github.com/php-coder/mystamps/issues/423) Most of our **checks on CI** now get executed only when files of a certain type were modified. This should give us a faster feedback loop. Checks are also being run when their configuration has been changed. If check performed by a maven plugin, it will be always run when `pom.xml` is modified. The same logic applies to the tools that are being installed from the `.travis.yml` file. Unfortunately, we have to unconditionally run checks even if a change in a file wasn't related to the plugin/tool configuration. Also there is no way to disable skipping logic and if you need to run a specific check there is no way to force its execution. I was thinking about introducing an environment variable or using a special magic comment from a commit message but I decided to leave it as-is for a now (although it can be added later). Commits: [7da91a53](https://github.com/php-coder/mystamps/commit/7da91a53a1d7f43670d67adfce359814fa7ee27a) |
 | 29.05.2017 Workaround | [php-coder/mystamps#588](https://github.com/php-coder/mystamps/issues/588) In order to import **test image** into database I had to move the image file from `src/test/resources` to `src/main/resources` directory because **Liquibase** is executing during the startup and it doesn't distinguish between test and main resources (it just searches in a class path). Commits: [646bb167](https://github.com/php-coder/mystamps/commit/646bb16706d3dc41fe8d613f101ac6679ac5cc92) |
+| 08.04.2017 Decision | At present we have 4 tests that are failing time to time. Until we fix them completely, they might fail builds and show PRs as having errors. Because **flaky tests** don't relate to code from PRs, this fact might frustrate contributors. To improve this situation I introduced **a special tag `unstable`** that can be added to flaky tests to ignore their failures. Commits: [56e848f7](https://github.com/php-coder/mystamps/commit/56e848f73b7a06691b886d4be156e3f95752afc0) |
 | 06.01.2017 Workaround | [php-coder/mystamps#434](https://github.com/php-coder/mystamps/issues/434) I was needed to render categories with its subcategories. Database returns data in a form (sub category name + category name or null). It turns out that it's impossible to render this data with **Thymeleaf** as a `<select>` with `<optgroup>` elements. I had to do data transformation inside of a service method. Commits: [b7fe1dac](https://github.com/php-coder/mystamps/commit/b7fe1dac7a7f0bc09e9e153a8408687fd899c79f) Example: https://gist.github.com/php-coder/d3020e4d8d00b8c5befe755c46f06f1b |
 | 28.09.2016 Workaround | Because **Travis CI** has **MySQL** version 5.5.53 (that is less than 5.6.5 but the latest for Ubuntu 12.04), we couldn't create a column with `NOW()` as a default value. We did the same in 3 steps to support this old version. Commits: [d55cd6cc](https://github.com/php-coder/mystamps/commit/d55cd6cc0842bc938c5c30f9aaaf78697ba84f45), [566d72f0](https://github.com/php-coder/mystamps/commit/566d72f053d785afb58234a6c7d69510a35bb7c4) |
 | 30.01.2016 Workaround | **html5validator** complained about `An "img" element must have an "alt" attribute`. I've suppressed this error until [php-coder/mystamps#314](https://github.com/php-coder/mystamps/issues/314) is fixed. Commits: [ec40a6ad](https://github.com/php-coder/mystamps/commit/ec40a6ad431b77c922195bd3225a4963416cea43) |