diff --git a/test/core/joining_segments.spec b/test/core/joining_segments.spec
new file mode 100755
index 00000000..708e9bf1
--- /dev/null
+++ b/test/core/joining_segments.spec
@@ -0,0 +1,187 @@
+#!/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=$0
+
+function setUp() {
+  export TERM="xterm-256color"
+  # Load Powerlevel9k
+  source powerlevel9k.zsh-theme
+}
+
+function testLeftNormalSegmentsShouldNotBeJoined() {
+  local -a POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(custom_world1 custom_world2 custom_world3 custom_world4_joined custom_world5 custom_world6)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo world2"
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD4="echo world4"
+  local POWERLEVEL9K_CUSTOM_WORLD5="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD6="echo world6"
+  
+  assertEquals "%K{white} %F{black}world1 %K{white}%F{black} %F{black}world2 %K{white}%F{black} %F{black}world4 %K{white}%F{black} %F{black}world6 %k%F{white}%f " "$(build_left_prompt)"
+}
+
+function testLeftJoinedSegments() {
+  local -a POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(custom_world1 custom_world2_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo world2"
+
+  assertEquals "%K{white} %F{black}world1 %K{white}%F{black}%F{black}world2 %k%F{white}%f " "$(build_left_prompt)"
+}
+
+function testLeftTransitiveJoinedSegments() {
+  local -a POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(custom_world1 custom_world2_joined custom_world3_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo world2"
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo world3"
+
+  assertEquals "%K{white} %F{black}world1 %K{white}%F{black}%F{black}world2 %K{white}%F{black}%F{black}world3 %k%F{white}%f " "$(build_left_prompt)"
+}
+
+function testLeftTransitiveJoiningWithConditionalJoinedSegment() {
+  local -a POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(custom_world1 custom_world2_joined custom_world3_joined custom_world4_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo world2"
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD4="echo world4"
+
+  assertEquals "%K{white} %F{black}world1 %K{white}%F{black}%F{black}world2 %K{white}%F{black}%F{black}world4 %k%F{white}%f " "$(build_left_prompt)"
+}
+
+function testLeftPromotingSegmentWithConditionalPredecessor() {
+  local -a POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(custom_world1 custom_world2 custom_world3_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo world3"
+
+  assertEquals "%K{white} %F{black}world1 %K{white}%F{black} %F{black}world3 %k%F{white}%f " "$(build_left_prompt)"
+}
+
+function testLeftPromotingSegmentWithJoinedConditionalPredecessor() {
+  local -a POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(custom_world1 custom_world2 custom_world3_joined custom_world4_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD4="echo world4"
+
+  assertEquals "%K{white} %F{black}world1 %K{white}%F{black} %F{black}world4 %k%F{white}%f " "$(build_left_prompt)"
+}
+
+function testLeftPromotingSegmentWithDeepJoinedConditionalPredecessor() {
+  local -a POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(custom_world1 custom_world2 custom_world3_joined custom_world4_joined custom_world5_joined custom_world6_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD4="echo world4"
+  local POWERLEVEL9K_CUSTOM_WORLD5="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD6="echo world6"
+
+  assertEquals "%K{white} %F{black}world1 %K{white}%F{black} %F{black}world4 %K{white}%F{black}%F{black}world6 %k%F{white}%f " "$(build_left_prompt)"
+}
+
+function testLeftJoiningBuiltinSegmentWorks() {
+  local -a POWERLEVEL9K_LEFT_PROMPT_ELEMENTS
+  POWERLEVEL9K_LEFT_PROMPT_ELEMENTS=(php_version php_version_joined)
+  alias php="echo PHP 1.2.3"
+
+  assertEquals "%K{013} %F{255}PHP 1.2.3 %K{013}%F{255}%F{255}PHP 1.2.3 %k%F{fuchsia}%f " "$(build_left_prompt)"
+
+  unalias php
+}
+
+function testRightNormalSegmentsShouldNotBeJoined() {
+  local -a POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS
+  POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(custom_world1 custom_world2 custom_world3 custom_world4 custom_world5_joined custom_world6)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo world2"
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD4="echo world4"
+  local POWERLEVEL9K_CUSTOM_WORLD5="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD6="echo world6"
+
+  assertEquals "%F{white}%f%K{white}%F{black} world1 %f%F{black}%f%K{white}%F{black} world2 %f%F{black}%f%K{white}%F{black} world4 %f%F{black}%f%K{white}%F{black} world6%E" "$(build_right_prompt)"
+}
+
+function testRightJoinedSegments() {
+  local -a POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS
+  POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(custom_world1 custom_world2_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo world2"
+
+  assertEquals "%F{white}%f%K{white}%F{black} world1 %f%K{white}%F{black}world2%E" "$(build_right_prompt)"
+}
+
+function testRightTransitiveJoinedSegments() {
+  local -a POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS
+  POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(custom_world1 custom_world2_joined custom_world3_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo world2"
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo world3"
+
+  assertEquals "%F{white}%f%K{white}%F{black} world1 %f%K{white}%F{black}world2 %f%K{white}%F{black}world3%E" "$(build_right_prompt)"
+}
+
+function testRightTransitiveJoiningWithConditionalJoinedSegment() {
+  local -a POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS
+  POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(custom_world1 custom_world2_joined custom_world3_joined custom_world4_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo world2"
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD4="echo world4"
+
+  assertEquals "%F{white}%f%K{white}%F{black} world1 %f%K{white}%F{black}world2 %f%K{white}%F{black}world4%E" "$(build_right_prompt)"
+}
+
+function testRightPromotingSegmentWithConditionalPredecessor() {
+  local -a POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS
+  POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(custom_world1 custom_world2 custom_world3_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo world3"
+
+  assertEquals "%F{white}%f%K{white}%F{black} world1 %f%F{black}%f%K{white}%F{black} world3%E" "$(build_right_prompt)"
+}
+
+function testRightPromotingSegmentWithJoinedConditionalPredecessor() {
+  local -a POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS
+  POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(custom_world1 custom_world2 custom_world3_joined custom_world4_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD4="echo world4"
+
+  assertEquals "%F{white}%f%K{white}%F{black} world1 %f%F{black}%f%K{white}%F{black} world4%E" "$(build_right_prompt)"
+}
+
+function testRightPromotingSegmentWithDeepJoinedConditionalPredecessor() {
+  local -a POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS
+  POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(custom_world1 custom_world2 custom_world3_joined custom_world4_joined custom_world5_joined custom_world6_joined)
+  local POWERLEVEL9K_CUSTOM_WORLD1="echo world1"
+  local POWERLEVEL9K_CUSTOM_WORLD2="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD3="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD4="echo world4"
+  local POWERLEVEL9K_CUSTOM_WORLD5="echo " # Print nothing to simulate unmet conditions
+  local POWERLEVEL9K_CUSTOM_WORLD6="echo world6"
+
+  assertEquals "%F{white}%f%K{white}%F{black} world1 %f%F{black}%f%K{white}%F{black} world4 %f%K{white}%F{black}world6%E" "$(build_right_prompt)"
+}
+
+function testRightJoiningBuiltinSegmentWorks() {
+  local -a POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS
+  POWERLEVEL9K_RIGHT_PROMPT_ELEMENTS=(php_version php_version_joined)
+  alias php="echo PHP 1.2.3"
+
+  assertEquals "%F{013}%f%K{013}%F{255} PHP 1.2.3 %f%K{013}%F{255}PHP 1.2.3%E" "$(build_right_prompt)"
+
+  unalias php
+}
+source shunit2/source/2.1/src/shunit2
\ No newline at end of file