More tests for 14.longest-common-prefix.jl

Author: GHTaarn

test/problems/14.longest-common-prefix.jl

@@ -2,4 +2,7 @@
     @test longest_common_prefix(["flower", "flow", "flight"]) == "fl"
     @test longest_common_prefix(["dog", "racecar", "car"]) == ""
     @test longest_common_prefix(["reflower", "flow", "flight"]) == ""
+    @test longest_common_prefix(["abc"]) == "abc"
+    @test longest_common_prefix(fill("abc", 5)) == "abc"
+    @test longest_common_prefix(fill("", 4)) == ""
 end