Add tests for `rust_version`

.travis.yml

@@ -22,4 +22,5 @@ script:
   - test/functions/utilities.spec
   - test/functions/colors.spec
   - test/segments/dir.spec
+  - test/segments/rust_version.spec
 

test/segments/rust_version.spec

@@ -0,0 +1,40 @@
+#!/usr/bin/env zsh
+#vim:ft=zsh ts=2 sw=2 sts=2 et fenc=utf-8
+
+# Required for shunit2 to run correctly
+setopt shwordsplit
+SHUNIT_PARENT=$0
+
+function setUp() {
+  export TERM="xterm-256color"
+  # Load Powerlevel9k
+  source powerlevel9k.zsh-theme
+}
+
+function mockRust() {
+  echo 'rustc  0.4.1a-alpha'
+}
+
+function testRust() {
+  alias rustc=mockRust
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(rust_version)
+
+  assertEquals "%K{208} %F{black}Rust 0.4.1a-alpha %k%F{208}%f " "$(build_left_prompt)"
+
+  unset POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  unalias rustc
+}
+
+function testRustPrintsNothingIfRustIsNotAvailable() {
+  alias rustc=noRust
+  POWERLEVEL9K_CUSTOM_WORLD='echo world'
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(custom_world rust_version)
+
+  assertEquals "%K{white} %F{black}world %k%F{white}%f " "$(build_left_prompt)"
+
+  unset POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  unset POWERLEVEL9K_CUSTOM_WORLD
+  unalias rustc
+}
+
+source shunit2/source/2.1/src/shunit2