diff --git a/src/cli.rs b/src/cli.rs
index 12a6357..faba4a5 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -9,13 +9,14 @@ type Error = crate::errors::CliError<AppConfigBuilderError>;
 
 const DEFAULT_MAX_CONN: usize = 8;
 
-#[derive(derive_builder::Builder)]
+#[derive(derive_builder::Builder, Debug)]
 pub struct AppConfig {
     /// Article urls
     pub urls: Vec<String>,
     pub max_conn: usize,
     /// Path to file of multiple articles into a single article
     pub merged: Option<String>,
+    // TODO: Change type to Path
     pub output_directory: Option<String>,
     pub log_level: LogLevel,
     pub can_disable_progress_bar: bool,
@@ -95,7 +96,7 @@ impl<'a> TryFrom<ArgMatches<'a>> for AppConfig {
                 None => DEFAULT_MAX_CONN,
             })
             .merged(arg_matches.value_of("output-name").map(|name| {
-                let file_ext = format!(".{}", arg_matches.value_of("export").unwrap());
+                let file_ext = format!(".{}", arg_matches.value_of("export").unwrap_or("epub"));
                 if name.ends_with(&file_ext) {
                     name.to_owned()
                 } else {
@@ -132,10 +133,11 @@ impl<'a> TryFrom<ArgMatches<'a>> for AppConfig {
             )
             .output_directory(
                 arg_matches
-                    .value_of("output_directory")
+                    .value_of("output-directory")
                     .map(|output_directory| {
                         let path = Path::new(output_directory);
                         if !path.exists() {
+                            // TODO: Create the directory
                             Err(Error::OutputDirectoryNotExists)
                         } else if !path.is_dir() {
                             Err(Error::WrongOutputDirectory)
@@ -157,14 +159,24 @@ impl<'a> TryFrom<ArgMatches<'a>> for AppConfig {
                 },
             )
             .export_type({
-                let export_type = arg_matches.value_of("export").unwrap();
+                let export_type = arg_matches.value_of("export").unwrap_or("epub");
                 if export_type == "html" {
                     ExportType::HTML
                 } else {
                     ExportType::EPUB
                 }
             })
-            .is_inlining_images(arg_matches.is_present("inline-images"))
+            .is_inlining_images(
+                (if arg_matches.is_present("inline-images") {
+                    if arg_matches.value_of("export") == Some("html") {
+                        Ok(true)
+                    } else {
+                        Err(Error::WrongExportInliningImages)
+                    }
+                } else {
+                    Ok(false)
+                })?,
+            )
             .try_init()
     }
 }
@@ -190,3 +202,134 @@ pub enum ExportType {
     HTML,
     EPUB,
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_clap_config_errors() {
+        let yaml_config = load_yaml!("cli_config.yml");
+        let app = App::from_yaml(yaml_config);
+
+        // It returns Ok when only a url is passed
+        let result = app
+            .clone()
+            .get_matches_from_safe(vec!["paperoni", "http://example.org"]);
+        assert!(result.is_ok());
+
+        // It returns an error when no args are passed
+        let result = app.clone().get_matches_from_safe(vec!["paperoni"]);
+        assert!(result.is_err());
+        assert_eq!(
+            clap::ErrorKind::MissingArgumentOrSubcommand,
+            result.unwrap_err().kind
+        );
+
+        // It returns an error when both output-dir and merge are used
+        let result = app.clone().get_matches_from_safe(vec![
+            "paperoni",
+            "http://example.org",
+            "--merge",
+            "foo",
+            "--output-dir",
+            "~",
+        ]);
+        assert!(result.is_err());
+        assert_eq!(clap::ErrorKind::ArgumentConflict, result.unwrap_err().kind);
+
+        // It returns an error when both no-css and no-header-css are used
+        let result = app.clone().get_matches_from_safe(vec![
+            "paperoni",
+            "http://example.org",
+            "--no-css",
+            "--no-header-css",
+        ]);
+        assert!(result.is_err());
+        assert_eq!(clap::ErrorKind::ArgumentConflict, result.unwrap_err().kind);
+
+        // It returns an error when inline-toc is used without merge
+        let result = app.clone().get_matches_from_safe(vec![
+            "paperoni",
+            "http://example.org",
+            "--inline-toc",
+        ]);
+        assert!(result.is_err());
+        assert_eq!(
+            clap::ErrorKind::MissingRequiredArgument,
+            result.unwrap_err().kind
+        );
+
+        // It returns an error when inline-images is used without export
+        let result = app.clone().get_matches_from_safe(vec![
+            "paperoni",
+            "http://example.org",
+            "--inline-images",
+        ]);
+        assert!(result.is_err());
+        assert_eq!(
+            clap::ErrorKind::MissingRequiredArgument,
+            result.unwrap_err().kind
+        );
+
+        // It returns an error when export is given an invalid value
+        let result = app.clone().get_matches_from_safe(vec![
+            "paperoni",
+            "http://example.org",
+            "--export",
+            "pdf",
+        ]);
+        assert!(result.is_err());
+        assert_eq!(clap::ErrorKind::InvalidValue, result.unwrap_err().kind);
+
+        // It returns an error when a max-conn is given a negative number.
+        let result = app.clone().get_matches_from_safe(vec![
+            "paperoni",
+            "http://example.org",
+            "--max-conn",
+            "-1",
+        ]);
+        assert!(result.is_err());
+        // The cli is configured not to accept negative numbers so passing "-1" would have it be read as a flag called 1
+        assert_eq!(clap::ErrorKind::UnknownArgument, result.unwrap_err().kind);
+    }
+
+    #[test]
+    fn test_init_with_cli() {
+        let yaml_config = load_yaml!("cli_config.yml");
+        let app = App::from_yaml(yaml_config);
+
+        // It returns an error when the urls passed are whitespace
+        let matches = app.clone().get_matches_from(vec!["paperoni", ""]);
+        let app_config = AppConfig::try_from(matches);
+        assert!(app_config.is_err());
+        assert_eq!(Error::NoUrls, app_config.unwrap_err());
+
+        // It returns an error when inline-toc is used when exporting to HTML
+        let matches = app.clone().get_matches_from(vec![
+            "paperoni",
+            "http://example.org",
+            "--merge",
+            "foo",
+            "--export",
+            "html",
+            "--inline-toc",
+        ]);
+        let app_config = AppConfig::try_from(matches);
+        assert!(app_config.is_err());
+        assert_eq!(Error::WrongExportInliningToC, app_config.unwrap_err());
+        // It returns an Ok when inline-toc is used when exporting to epub
+        let matches = app.clone().get_matches_from(vec![
+            "paperoni",
+            "http://example.org",
+            "--merge",
+            "foo",
+            "--export",
+            "epub",
+            "--inline-toc",
+        ]);
+        assert!(AppConfig::try_from(matches).is_ok());
+
+        // It returns an error when inline-images is used when exporting to epub
+    }
+}
diff --git a/src/cli_config.yml b/src/cli_config.yml
index 4f86d52..8de70e1 100644
--- a/src/cli_config.yml
+++ b/src/cli_config.yml
@@ -12,7 +12,7 @@ args:
       long: file
       help: Input file containing links
       takes_value: true
-  - output_directory:
+  - output-directory:
       short: o
       long: output-dir
       help: Directory to store output epub documents
@@ -70,7 +70,6 @@ args:
       possible_values: [html, epub]
       value_name: type
       takes_value: true
-      default_value: epub
   - inline-images:
       long: inline-images
       help: Inlines the article images when exporting to HTML using base64. Pass --help to learn more.
diff --git a/src/errors.rs b/src/errors.rs
index 8fbfeea..c615477 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -138,6 +138,14 @@ pub enum LogError {
     CreateLogDirectoryError(#[from] std::io::Error),
 }
 
+// dumb hack to allow for comparing errors in testing.
+// derive macros cannot be used because underlying errors like io::Error do not derive PartialEq
+impl PartialEq for LogError {
+    fn eq(&self, other: &Self) -> bool {
+        format!("{:?}", self) == format!("{:?}", other)
+    }
+}
+
 #[derive(Debug, Error)]
 pub enum CliError<BuilderError: Debug + Display> {
     #[error("Failed to open file with urls: {0}")]
@@ -156,6 +164,16 @@ pub enum CliError<BuilderError: Debug + Display> {
     OutputDirectoryNotExists,
     #[error("Unable to start logger!\n{0}")]
     LogError(#[from] LogError),
-    #[error("The --inline-toc can only be used exporting to epub")]
+    #[error("The --inline-toc flag can only be used when exporting to epub")]
     WrongExportInliningToC,
+    #[error("The --inline-images flag can only be used when exporting to html")]
+    WrongExportInliningImages,
+}
+
+// dumb hack to allow for comparing errors in testing.
+// derive macros cannot be used because underlying errors like io::Error do not derive PartialEq
+impl<T: Debug + Display> PartialEq for CliError<T> {
+    fn eq(&self, other: &Self) -> bool {
+        format!("{:?}", self) == format!("{:?}", other)
+    }
 }
diff --git a/src/extractor.rs b/src/extractor.rs
index b16373a..fcd13a4 100644
--- a/src/extractor.rs
+++ b/src/extractor.rs
@@ -4,6 +4,7 @@ use kuchiki::{traits::*, NodeRef};
 use crate::errors::PaperoniError;
 use crate::moz_readability::{MetaData, Readability};
 
+/// A tuple of the url and an Option of the resource's MIME type
 pub type ResourceInfo = (String, Option<String>);
 
 pub struct Article {
diff --git a/src/html.rs b/src/html.rs
index 7b761d2..b43df6a 100644
--- a/src/html.rs
+++ b/src/html.rs
@@ -12,7 +12,7 @@ use kuchiki::{traits::*, NodeRef};
 use log::{debug, error, info};
 
 use crate::{
-    cli::{self, AppConfig},
+    cli::{self, AppConfig, CSSConfig},
     errors::PaperoniError,
     extractor::Article,
     moz_readability::MetaData,
@@ -91,38 +91,33 @@ pub fn generate_html_exports(
                     *id_attr = format!("readability-page-{}", idx);
                 }
 
-                for (img_url, mime_type_opt) in &article.img_urls {
-                    if app_config.is_inlining_images {
-                        info!("Inlining images for {}", title);
-                        let result = update_imgs_base64(
-                            article,
-                            img_url,
-                            mime_type_opt.as_deref().unwrap_or("image/*"),
-                        );
+                if app_config.is_inlining_images {
+                    info!("Inlining images for {}", title);
+                    let result = update_imgs_base64(article);
 
-                        if let Err(e) = result {
-                            let mut err: PaperoniError = e.into();
-                            err.set_article_source(title);
-                            error!("Unable to copy images to imgs dir for {}", title);
-                            errors.push(err);
-                        }
+                    if let Err(e) = result {
+                        let mut err: PaperoniError = e.into();
+                        err.set_article_source(title);
+                        error!("Unable to copy images to imgs dir for {}", title);
+                        errors.push(err);
+                    }
 
-                        info!("Completed inlining images for {}", title);
+                    info!("Completed inlining images for {}", title);
+                } else {
+                    info!("Copying images to imgs dir for {}", title);
+                    let result = update_img_urls(article, &imgs_dir_path).map_err(|e| {
+                        let mut err: PaperoniError = e.into();
+                        err.set_article_source(title);
+                        err
+                    });
+                    if let Err(e) = result {
+                        error!("Unable to copy images to imgs dir for {}", title);
+                        errors.push(e);
                     } else {
-                        info!("Copying images to imgs dir for {}", title);
-                        let result = update_img_urls(article, &imgs_dir_path).map_err(|e| {
-                            let mut err: PaperoniError = e.into();
-                            err.set_article_source(title);
-                            err
-                        });
-                        if let Err(e) = result {
-                            error!("Unable to copy images to imgs dir for {}", title);
-                            errors.push(e);
-                        } else {
-                            info!("Successfully copied images to imgs dir for {}", title);
-                        }
+                        info!("Successfully copied images to imgs dir for {}", title);
                     }
                 }
+
                 bar.inc(1);
                 successful_articles_table.add_row(vec![title]);
                 body_elem.as_node().append(article_elem.as_node().clone());
@@ -137,7 +132,8 @@ pub fn generate_html_exports(
                     .map(|article| (article.metadata(), article.url.as_str()))
                     .collect(),
             );
-            inline_css(&base_html_elem, app_config);
+            inline_css(&base_html_elem, &app_config.css_config);
+            remove_existing_stylesheet_link(&base_html_elem);
 
             info!("Added title, footer and inlined styles for {}", name);
 
@@ -199,13 +195,7 @@ pub fn generate_html_exports(
                     let mut out_file = File::create(&file_name)?;
 
                     if app_config.is_inlining_images {
-                        for (img_url, mime_type_opt) in &article.img_urls {
-                            update_imgs_base64(
-                                article,
-                                img_url,
-                                mime_type_opt.as_deref().unwrap_or("image/*"),
-                            )?
-                        }
+                        update_imgs_base64(article)?;
                     } else {
                         let base_path =
                             Path::new(app_config.output_directory.as_deref().unwrap_or("."));
@@ -233,7 +223,8 @@ pub fn generate_html_exports(
 
                     insert_title_elem(article.node_ref(), article.metadata().title());
                     insert_appendix(article.node_ref(), vec![(article.metadata(), &article.url)]);
-                    inline_css(article.node_ref(), app_config);
+                    inline_css(article.node_ref(), &app_config.css_config);
+                    remove_existing_stylesheet_link(article.node_ref());
 
                     article.node_ref().serialize(&mut out_file)?;
                     Ok(())
@@ -268,24 +259,26 @@ fn create_qualname(name: &str) -> QualName {
 }
 
 /// Updates the src attribute of `<img>` elements with a base64 encoded string of the image data
-fn update_imgs_base64(
-    article: &Article,
-    img_url: &str,
-    mime_type: &str,
-) -> Result<(), std::io::Error> {
+fn update_imgs_base64(article: &Article) -> Result<(), std::io::Error> {
     let temp_dir = std::env::temp_dir();
-    let img_path = temp_dir.join(img_url);
-    let img_bytes = std::fs::read(img_path)?;
-    let img_base64_str = format!("data:image:{};base64,{}", mime_type, encode(img_bytes));
+    for (img_url, mime_type) in &article.img_urls {
+        let img_path = temp_dir.join(img_url);
+        let img_bytes = std::fs::read(img_path)?;
+        let img_base64_str = format!(
+            "data:image:{};base64,{}",
+            mime_type.as_deref().unwrap_or("image/*"),
+            encode(img_bytes)
+        );
 
-    let img_elems = article
-        .node_ref()
-        .select(&format!("img[src=\"{}\"]", img_url))
-        .unwrap();
-    for img_elem in img_elems {
-        let mut img_attr = img_elem.attributes.borrow_mut();
-        if let Some(src_attr) = img_attr.get_mut("src") {
-            *src_attr = img_base64_str.clone();
+        let img_elems = article
+            .node_ref()
+            .select(&format!("img[src=\"{}\"]", img_url))
+            .unwrap();
+        for img_elem in img_elems {
+            let mut img_attr = img_elem.attributes.borrow_mut();
+            if let Some(src_attr) = img_attr.get_mut("src") {
+                *src_attr = img_base64_str.clone();
+            }
         }
     }
     Ok(())
@@ -344,18 +337,23 @@ fn insert_appendix(root_node: &NodeRef, article_links: Vec<(&MetaData, &str)>) {
             format!("<a href=\"{}\">{}</a><br></br>", url, article_name)
         })
         .collect();
-    let footer_inner_html = format!("<h2>Appendix</h2><h2>Article sources</h3>{}", link_tags);
-    let footer_elem =
-        kuchiki::parse_fragment(create_qualname("footer"), Vec::new()).one(footer_inner_html);
-    root_node.append(footer_elem);
+    let footer_inner_html = format!(
+        "<footer><h2>Appendix</h2><h3>Article sources</h3>{}</footer>",
+        link_tags
+    );
+    let footer_container =
+        kuchiki::parse_fragment(create_qualname("div"), Vec::new()).one(footer_inner_html);
+    let footer_elem = footer_container.select_first("footer").unwrap();
+
+    root_node.append(footer_elem.as_node().clone());
 }
 
 /// Inlines the CSS stylesheets into the HTML article node
-fn inline_css(root_node: &NodeRef, app_config: &AppConfig) {
+fn inline_css(root_node: &NodeRef, css_config: &CSSConfig) {
     let body_stylesheet = include_str!("./assets/body.min.css");
     let header_stylesheet = include_str!("./assets/headers.min.css");
     let mut css_str = String::new();
-    match app_config.css_config {
+    match css_config {
         cli::CSSConfig::NoHeaders => {
             css_str.push_str(body_stylesheet);
         }
@@ -371,21 +369,118 @@ fn inline_css(root_node: &NodeRef, app_config: &AppConfig) {
     let style_container =
         kuchiki::parse_fragment(create_qualname("div"), Vec::new()).one(css_html_str);
     let style_elem = style_container.select_first("style").unwrap();
-    match root_node.select_first("head") {
-        Ok(head_elem) => {
-            head_elem.as_node().prepend(style_elem.as_node().to_owned());
-        }
-        Err(_) => {
-            debug!("{}", HEAD_ELEM_NOT_FOUND);
-            let html_elem = root_node.select_first("html").unwrap();
-            let head_elem = NodeRef::new_element(create_qualname("head"), BTreeMap::new());
-            head_elem.prepend(style_elem.as_node().to_owned());
-            html_elem.as_node().prepend(head_elem);
-        }
-    }
+    let head_elem = root_node.select_first("head").expect(HEAD_ELEM_NOT_FOUND);
+    head_elem.as_node().prepend(style_elem.as_node().to_owned());
+}
 
-    // Remove the <link> of the stylesheet since styles are now inlined
+/// Removes the <link> of the stylesheet. This is used when inlining styles
+fn remove_existing_stylesheet_link(root_node: &NodeRef) {
     if let Ok(style_link_elem) = root_node.select_first("link[href=\"stylesheet.css\"]") {
         style_link_elem.as_node().detach();
     };
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    #[test]
+    fn test_insert_title_elem() {
+        let title = "Sample title";
+        let html_str = r#"<html><head><meta charset="UTF-8"/></head><body></body></html>"#;
+        let doc = kuchiki::parse_html().one(html_str);
+        assert_eq!(0, doc.select("title").unwrap().count());
+
+        insert_title_elem(&doc, title);
+        assert_eq!(1, doc.select("title").unwrap().count());
+        assert_eq!(title, doc.select_first("title").unwrap().text_contents());
+    }
+
+    #[test]
+    fn test_create_qualname() {
+        let name = "div";
+        assert_eq!(
+            create_qualname(name),
+            QualName::new(
+                None,
+                Namespace::from("http://www.w3.org/1999/xhtml"),
+                LocalName::from(name)
+            )
+        );
+    }
+
+    #[test]
+    fn test_inline_css() {
+        let html_str = r#"<html>
+        <head><meta charset="UTF-8"/></head>
+        <body>
+            <p>Lorem ipsum sample text goes here.</p>
+        </body>
+        </html>"#;
+        let doc = kuchiki::parse_html().one(html_str);
+        let body_stylesheet = include_str!("./assets/body.min.css");
+        let header_stylesheet = include_str!("./assets/headers.min.css");
+        assert_eq!(0, doc.select("style").unwrap().count());
+
+        inline_css(&doc, &CSSConfig::None);
+        assert_eq!(0, doc.select("style").unwrap().count());
+
+        inline_css(&doc, &CSSConfig::NoHeaders);
+        assert_eq!(1, doc.select("style").unwrap().count());
+        let style_elem = doc.select_first("style").unwrap();
+        assert_eq!(body_stylesheet, style_elem.text_contents());
+
+        let doc = kuchiki::parse_html().one(html_str);
+        inline_css(&doc, &CSSConfig::All);
+        assert_eq!(1, doc.select("style").unwrap().count());
+        let style_elem = doc.select_first("style").unwrap();
+        assert_eq!(
+            format!("{}{}", body_stylesheet, header_stylesheet),
+            style_elem.text_contents()
+        );
+    }
+
+    #[test]
+    fn test_remove_existing_stylesheet_link() {
+        let html_str = r#"<html>
+        <head><link href="stylesheet.css"></link></head>
+        <body><p>Lorem ipsum sample text goes here.</p></body></html>"#;
+        let doc = kuchiki::parse_html().one(html_str);
+        assert_eq!(1, doc.select("link").unwrap().count());
+        remove_existing_stylesheet_link(&doc);
+        assert_eq!(0, doc.select("link").unwrap().count());
+    }
+
+    #[test]
+    fn test_insert_appendix() {
+        let html_str = r#"<html>
+        <head><meta charset="UTF-8"/></head>
+        <body>
+            <p>Lorem ipsum sample text goes here.</p>
+        </body>
+        </html>"#;
+        let doc = kuchiki::parse_html().one(html_str);
+        let meta_data = MetaData::new();
+
+        assert_eq!(0, doc.select("footer").unwrap().count());
+
+        insert_appendix(&doc, vec![(&meta_data, "http://example.org")]);
+
+        assert_eq!(1, doc.select("footer").unwrap().count());
+        assert_eq!(1, doc.select("footer > h2").unwrap().count());
+        assert_eq!(
+            "Appendix",
+            doc.select_first("footer > h2").unwrap().text_contents()
+        );
+        assert_eq!(1, doc.select("footer > h3").unwrap().count());
+        assert_eq!(
+            "Article sources",
+            doc.select_first("footer > h3").unwrap().text_contents()
+        );
+        assert_eq!(1, doc.select("a").unwrap().count());
+
+        let anchor_elem = doc.select_first("a").unwrap();
+        assert_eq!("http://example.org", anchor_elem.text_contents());
+        let anchor_attrs = anchor_elem.attributes.borrow();
+        assert_eq!(Some("http://example.org"), anchor_attrs.get("href"));
+    }
+}
diff --git a/src/http.rs b/src/http.rs
index 15cdb3c..1a1206d 100644
--- a/src/http.rs
+++ b/src/http.rs
@@ -150,6 +150,15 @@ async fn process_img_response<'a>(
     let img_mime = img_response
         .content_type()
         .map(|mime| mime.essence().to_string());
+    if let Some(mime_str) = &img_mime {
+        if !mime_str.starts_with("image/") {
+            return Err(ErrorKind::HTTPError(format!(
+                "Invalid image MIME type: {} for {}",
+                mime_str, url
+            ))
+            .into());
+        }
+    }
     let img_ext = match img_response
         .content_type()
         .map(|mime| map_mime_subtype_to_ext(mime.subtype()).to_string())