diff --git a/src/postprocessors.rs b/src/postprocessors.rs
index 5537b00..2ca4183 100644
--- a/src/postprocessors.rs
+++ b/src/postprocessors.rs
@@ -23,26 +23,84 @@ pub fn filter_by_tags(
     only_tags: Vec<String>,
 ) -> impl Fn(&mut Context, &mut MarkdownEvents) -> PostprocessorResult {
     move |context: &mut Context, _events: &mut MarkdownEvents| -> PostprocessorResult {
-        if !skip_tags.is_empty() || !only_tags.is_empty() {
-            match context.frontmatter.get("tags") {
-                Some(Value::Sequence(tags)) => {
-                    let skip = skip_tags
-                        .iter()
-                        .any(|tag| tags.contains(&Value::String(tag.to_string())));
-                    let include = only_tags.is_empty()
-                        || only_tags
-                            .iter()
-                            .any(|tag| tags.contains(&Value::String(tag.to_string())));
-                    if skip || !include {
-                        PostprocessorResult::StopAndSkipNote
-                    } else {
-                        PostprocessorResult::Continue
-                    }
-                }
-                _ => PostprocessorResult::Continue,
-            }
-        } else {
-            PostprocessorResult::Continue
+        match context.frontmatter.get("tags") {
+            None => filter_by_tags_(&[], &skip_tags, &only_tags),
+            Some(Value::Sequence(tags)) => filter_by_tags_(tags, &skip_tags, &only_tags),
+            _ => PostprocessorResult::Continue,
         }
     }
 }
+
+fn filter_by_tags_(
+    tags: &[Value],
+    skip_tags: &[String],
+    only_tags: &[String],
+) -> PostprocessorResult {
+    let skip = skip_tags
+        .iter()
+        .any(|tag| tags.contains(&Value::String(tag.to_string())));
+    let include = only_tags.is_empty()
+        || only_tags
+            .iter()
+            .any(|tag| tags.contains(&Value::String(tag.to_string())));
+
+    if skip || !include {
+        PostprocessorResult::StopAndSkipNote
+    } else {
+        PostprocessorResult::Continue
+    }
+}
+
+#[test]
+fn test_filter_tags() {
+    let tags = vec![
+        Value::String("skip".to_string()),
+        Value::String("publish".to_string()),
+    ];
+    let empty_tags = vec![];
+    assert_eq!(
+        filter_by_tags_(&empty_tags, &[], &[]),
+        PostprocessorResult::Continue,
+        "When no exclusion & inclusion are specified, files without tags are included"
+    );
+    assert_eq!(
+        filter_by_tags_(&tags, &[], &[]),
+        PostprocessorResult::Continue,
+        "When no exclusion & inclusion are specified, files with tags are included"
+    );
+    assert_eq!(
+        filter_by_tags_(&tags, &["exclude".to_string()], &[]),
+        PostprocessorResult::Continue,
+        "When exclusion tags don't match files with tags are included"
+    );
+    assert_eq!(
+        filter_by_tags_(&empty_tags, &["exclude".to_string()], &[]),
+        PostprocessorResult::Continue,
+        "When exclusion tags don't match files without tags are included"
+    );
+    assert_eq!(
+        filter_by_tags_(&tags, &[], &["publish".to_string()]),
+        PostprocessorResult::Continue,
+        "When exclusion tags don't match files with tags are included"
+    );
+    assert_eq!(
+        filter_by_tags_(&empty_tags, &[], &["include".to_string()]),
+        PostprocessorResult::StopAndSkipNote,
+        "When inclusion tags are specified files without tags are excluded"
+    );
+    assert_eq!(
+        filter_by_tags_(&tags, &[], &["include".to_string()]),
+        PostprocessorResult::StopAndSkipNote,
+        "When exclusion tags don't match files with tags are exluded"
+    );
+    assert_eq!(
+        filter_by_tags_(&tags, &["skip".to_string()], &["skip".to_string()]),
+        PostprocessorResult::StopAndSkipNote,
+        "When both inclusion and exclusion tags are the same exclusion wins"
+    );
+    assert_eq!(
+        filter_by_tags_(&tags, &["skip".to_string()], &["publish".to_string()]),
+        PostprocessorResult::StopAndSkipNote,
+        "When both inclusion and exclusion tags match exclusion wins"
+    );
+}
diff --git a/tests/testdata/expected/filter-by-tags/no-frontmatter.md b/tests/testdata/expected/filter-by-tags/no-frontmatter.md
deleted file mode 100644
index 427b0ea..0000000
--- a/tests/testdata/expected/filter-by-tags/no-frontmatter.md
+++ /dev/null
@@ -1 +0,0 @@
-A note without frontmatter should be exported.
diff --git a/tests/testdata/expected/filter-by-tags/no-tags.md b/tests/testdata/expected/filter-by-tags/no-tags.md
deleted file mode 100644
index fdc5f81..0000000
--- a/tests/testdata/expected/filter-by-tags/no-tags.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-title: foo
----
-
-A public note.