diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index f76e374..49cfa50 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -12,20 +12,20 @@ jobs:
   build:
     name: Test on OTP ${{ matrix.otp_version }} and ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
+    container:
+      image: erlang:${{matrix.otp_version}}
 
     strategy:
       matrix:
-        otp_version: ['23.2.1', '22.3.4.2', '21.3.8.16', '20.3.8.21', '19.3.6.13']
+        otp_version: ['23.2', '22.3', '21.3', '20.3', '19.3']
         os: [ubuntu-latest]
 
     steps:
     - uses: actions/checkout@v2
 
-    - uses: bajankristof/setup-erlang@master
-      with:
-        otp-version: ${{ matrix.otp_version }}
-
     - name: Compile
       run: rebar3 compile
+    - name: Dialyze
+      run: rebar3 as test dialyzer
     - name: EUnit tests
       run: TERM=xterm rebar3 eunit
diff --git a/.gitignore b/.gitignore
index e8f4b5a..d306af0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,5 +12,7 @@ _build
 erl_crash.dump
 *.pyc
 *~
+TEST-*.xml
+/foo
 
 src/ec_semver_parser.peg
diff --git a/src/ec_git_vsn.erl b/src/ec_git_vsn.erl
index 569d78c..c932c58 100644
--- a/src/ec_git_vsn.erl
+++ b/src/ec_git_vsn.erl
@@ -34,7 +34,7 @@
 new() ->
     {}.
 
--spec vsn(t()) -> {ok, string()} | {error, Reason::any()}.
+-spec vsn(t()|string()) -> {ok, string()} | {error, Reason::any()}.
 vsn(Data) ->
     {Vsn, RawRef, RawCount} = collect_default_refcount(Data),
     {ok, build_vsn_string(Vsn, RawRef, RawCount)}.
@@ -61,12 +61,7 @@ collect_default_refcount(Data) ->
 build_vsn_string(Vsn, RawRef, RawCount) ->
     %% Cleanup the tag and the Ref information. Basically leading 'v's and
     %% whitespace needs to go away.
-    RefTag = case RawRef of
-                 undefined ->
-                     "";
-                 RawRef ->
-                     [".ref", re:replace(RawRef, "\\s", "", [global])]
-             end,
+    RefTag = [".ref", re:replace(RawRef, "\\s", "", [global])],
     Count = erlang:iolist_to_binary(re:replace(RawCount, "\\s", "", [global])),
 
     %% Create the valid [semver](http://semver.org) version from the tag
@@ -82,26 +77,48 @@ get_patch_count(RawRef) ->
     Ref = re:replace(RawRef, "\\s", "", [global]),
     Cmd = io_lib:format("git rev-list --count ~s..HEAD",
                          [Ref]),
-    os:cmd(Cmd).
+    case os:cmd(Cmd) of
+        "fatal: " ++ _ ->
+            0;
+        Count ->
+            Count
+    end.
 
--spec parse_tags(t()) -> {string()|undefined, ec_semver:version_string()}.
+-spec parse_tags(t()|string()) -> {string()|undefined, ec_semver:version_string()}.
 parse_tags({}) ->
     parse_tags("");
 parse_tags(Pattern) ->
     Cmd = io_lib:format("git describe --abbrev=0 --tags --match \"~s*\"", [Pattern]),
     Tag = os:cmd(Cmd),
-    Vsn = slice(Tag, len(Pattern)),
-    Vsn1 = trim(trim(Vsn, left, "v"), right, "\n"),
-    {Tag, Vsn1}.
+    case Tag of
+        "fatal: " ++ _ ->
+            {undefined, ""};
+        _ ->
+            Vsn = slice(Tag, len(Pattern)),
+            Vsn1 = trim(trim(Vsn, left, "v"), right, "\n"),
+            {Tag, Vsn1}
+    end.
 
 -ifdef(unicode_str).
 len(Str) -> string:length(Str).
 trim(Str, right, Chars) -> string:trim(Str, trailing, Chars);
-trim(Str, left, Chars) -> string:trim(Str, leading, Chars);
-trim(Str, both, Chars) -> string:trim(Str, both, Chars).
+trim(Str, left, Chars) -> string:trim(Str, leading, Chars).
 slice(Str, Len) -> string:slice(Str, Len).
 -else.
 len(Str) -> string:len(Str).
 trim(Str, Dir, [Chars|_]) -> string:strip(Str, Dir, Chars).
 slice(Str, Len) -> string:substr(Str, Len + 1).
 -endif.
+
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+
+parse_tags_test() ->
+    ?assertEqual({undefined, ""}, parse_tags("a.b.c")).
+
+get_patch_count_test() ->
+    ?assertEqual(0, get_patch_count("a.b.c")).
+
+collect_default_refcount_test() ->
+    ?assertMatch({"", _, _}, collect_default_refcount("a.b.c")).
+-endif.
diff --git a/src/ec_talk.erl b/src/ec_talk.erl
index 36cff8e..454b1f8 100644
--- a/src/ec_talk.erl
+++ b/src/ec_talk.erl
@@ -199,8 +199,6 @@ get_string(String) ->
 
 -ifdef(unicode_str).
 trim(Str) -> string:trim(Str).
-trim(Str, right, Chars) -> string:trim(Str, trailing, Chars);
-trim(Str, left, Chars) -> string:trim(Str, leading, Chars);
 trim(Str, both, Chars) -> string:trim(Str, both, Chars).
 -else.
 trim(Str) -> string:strip(Str).