Test terminal can set dimensions

- ShellTest now has fields which can be used to
  change terminal default widht/height.
- Backed by properties so can be used with
  `spring.shell.test.terminal-width` and
  `spring.shell.test.terminal-height`.
- Backport #656
- Fixes #659

spring-shell-docs/src/main/asciidoc/using-shell-testing-basics.adoc

@@ -1,5 +1,5 @@
 [[using-shell-testing-basics]]
-==== Basics
+=== Basics
 ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
 
 Spring Shell provides a number of utilities and annotations to help when testing your application.

spring-shell-docs/src/main/asciidoc/using-shell-testing-settings.adoc

@@ -0,0 +1,27 @@
+[[using-shell-testing-settings]]
+=== Settings
+ifndef::snippets[:snippets: ../../test/java/org/springframework/shell/docs]
+
+Built in emulation uses terminal width 80 and height 24 on default.
+Changing dimensions is useful if output would span into multiple
+lines and you don't want to handle those cases in a tests.
+
+These can be changed using properties `spring.shell.test.terminal-width`
+or `spring.shell.test.terminal-height`.
+
+====
+[source, java, indent=0]
+----
+include::{snippets}/TestingSnippets.java[tag=testing-shelltest-dimensions-props]
+----
+====
+
+`ShellTest` annotation have fields `terminalWidth` and `terminalHeight`
+which can also be used to change dimensions.
+
+====
+[source, java, indent=0]
+----
+include::{snippets}/TestingSnippets.java[tag=testing-shelltest-dimensions-field]
+----
+====

spring-shell-docs/src/main/asciidoc/using-shell-testing.adoc

@@ -16,3 +16,5 @@ NOTE: Testing support is currently under development and will be
       unstable for various parts.
 
 include::using-shell-testing-basics.adoc[]
+
+include::using-shell-testing-settings.adoc[]

spring-shell-docs/src/test/java/org/springframework/shell/docs/TestingSnippets.java

@@ -81,4 +81,23 @@ class TestingSnippets {
 		}
 	}
 	// end::testing-shelltest-noninteractive[]
+
+	class Dump1 {
+
+		// tag::testing-shelltest-dimensions-props[]
+		@ShellTest(properties = {
+			"spring.shell.test.terminal-width=120",
+			"spring.shell.test.terminal-height=40"
+		})
+		class ShellSettingsSample {}
+		// end::testing-shelltest-dimensions-props[]
+	}
+	class Dump2 {
+
+		// tag::testing-shelltest-dimensions-field[]
+		@ShellTest(terminalWidth = 120, terminalHeight = 40)
+		class ShellSettingsSample {}
+		// end::testing-shelltest-dimensions-field[]
+	}
+
 }