RFR: Initial section on testing [v9]

[Jesper Wilhelmsson]

> It's a start.

Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:

  Added note about TEST.properties

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Changes:
  - all: https://git.openjdk.java.net/guide/pull/30/files
  - new: https://git.openjdk.java.net/guide/pull/30/files/2726d1dc..43dd2548

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=guide&pr=30&range=08
 - incr: https://webrevs.openjdk.java.net/?repo=guide&pr=30&range=07-08

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/guide/pull/30.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/30/head:pull/30

PR: https://git.openjdk.java.net/guide/pull/30