diff --git a/src/lib.rs b/src/lib.rs
index c2b7e2a..0cd59a6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,7 +6,10 @@ use mdbook::errors::Result;
 use mdbook::preprocess::{Preprocessor, PreprocessorContext};
 use mdbook::BookItem;
 
+use crate::utils::{FileReader, SystemFileReader};
+
 mod links;
+mod utils;
 
 const MAX_LINK_NESTED_DEPTH: usize = 10;
 
@@ -36,7 +39,13 @@ impl Preprocessor for Template {
                         .map(|dir| src_dir.join(dir))
                         .expect("All book items have a parent");
 
-                    let content = replace_template(&chapter.content, base, source, 0);
+                    let content = replace_template(
+                        &chapter.content,
+                        &SystemFileReader::default(),
+                        base,
+                        source,
+                        0,
+                    );
                     chapter.content = content;
                 }
             }
@@ -50,10 +59,17 @@ impl Preprocessor for Template {
     }
 }
 
-fn replace_template<P1, P2>(chapter_content: &str, base: P1, source: P2, depth: usize) -> String
+fn replace_template<P1, P2, FR>(
+    chapter_content: &str,
+    file_reader: &FR,
+    base: P1,
+    source: P2,
+    depth: usize,
+) -> String
 where
     P1: AsRef<Path>,
     P2: AsRef<Path>,
+    FR: FileReader,
 {
     let path = base.as_ref();
     let source = source.as_ref();
@@ -64,12 +80,13 @@ where
     for link in links::extract_template_links(chapter_content) {
         replaced.push_str(&chapter_content[previous_end_index..link.start_index]);
 
-        match link.replace_args(&path) {
+        match link.replace_args(&path, file_reader) {
             Ok(new_content) => {
                 if depth < MAX_LINK_NESTED_DEPTH {
                     if let Some(rel_path) = link.link_type.relative_path(path) {
                         replaced.push_str(&replace_template(
                             &new_content,
+                            file_reader,
                             rel_path,
                             source,
                             depth + 1,
@@ -99,4 +116,173 @@ where
 
     replaced.push_str(&chapter_content[previous_end_index..]);
     replaced
+}
+
+#[cfg(test)]
+mod lib_tests {
+    use std::collections::HashMap;
+    use std::path::PathBuf;
+
+    use crate::replace_template;
+    use crate::utils::TestFileReader;
+
+    #[test]
+    fn test_happy_path_escaped() {
+        let start = r"
+        Example Text
+        ```hbs
+        \{{#template template.md}} << an escaped link!
+        ```";
+        let end = r"
+        Example Text
+        ```hbs
+        {{#template template.md}} << an escaped link!
+        ```";
+
+        assert_eq!(
+            replace_template(start, &TestFileReader::default(), "", "", 0),
+            end
+        );
+    }
+
+    #[test]
+    fn test_happy_path_simple() {
+        let start_chapter_content = "{{#template footer.md}}";
+        let end_chapter_content = "Designed & Created With Love From - Goudham & Hazel";
+        let file_name = PathBuf::from("footer.md");
+        let template_file_contents =
+            "Designed & Created With Love From - Goudham & Hazel".to_string();
+        let map = HashMap::from([(file_name, template_file_contents)]);
+        let file_reader = &TestFileReader::from(map);
+
+        let actual_chapter_content =
+            replace_template(start_chapter_content, file_reader, "", "", 0);
+
+        assert_eq!(actual_chapter_content, end_chapter_content);
+    }
+
+    #[test]
+    fn test_happy_path_with_args() {
+        let start_chapter_content = "{{#template footer.md authors=Goudham & Hazel}}";
+        let end_chapter_content = "Designed & Created With Love From - Goudham & Hazel";
+        let file_name = PathBuf::from("footer.md");
+        let template_file_contents = "Designed & Created With Love From - {{$authors}}".to_string();
+        let map = HashMap::from([(file_name, template_file_contents)]);
+        let file_reader = &TestFileReader::from(map);
+
+        let actual_chapter_content =
+            replace_template(start_chapter_content, file_reader, "", "", 0);
+
+        assert_eq!(actual_chapter_content, end_chapter_content);
+    }
+
+    #[test]
+    fn test_happy_path_new_lines() {
+        let start_chapter_content = r"
+        Some content...
+        {{#template footer.md authors=Goudham & Hazel}}";
+        let end_chapter_content = r"
+        Some content...
+        - - - -
+        Designed & Created With Love From Goudham & Hazel";
+        let file_name = PathBuf::from("footer.md");
+        let template_file_contents = r"- - - -
+        Designed & Created With Love From {{$authors}}"
+            .to_string();
+        let map = HashMap::from([(file_name, template_file_contents)]);
+        let file_reader = &TestFileReader::from(map);
+
+        let actual_chapter_content =
+            replace_template(start_chapter_content, file_reader, "", "", 0);
+
+        assert_eq!(actual_chapter_content, end_chapter_content);
+    }
+
+    #[test]
+    fn test_happy_path_multiple() {
+        let start_chapter_content = r"
+        {{#template header.md title=Example Title}}
+        Some content...
+        {{#template 
+            footer.md 
+        authors=Goudham & Hazel}}";
+        let end_chapter_content = r"
+        # Example Title
+        Some content...
+        - - - -
+        Designed & Created With Love From Goudham & Hazel";
+        let header_file_name = PathBuf::from("header.md");
+        let header_contents = r"# {{$title}}".to_string();
+        let footer_file_name = PathBuf::from("footer.md");
+        let footer_contents = r"- - - -
+        Designed & Created With Love From {{$authors}}"
+            .to_string();
+        let map = HashMap::from([
+            (footer_file_name, footer_contents),
+            (header_file_name, header_contents),
+        ]);
+        let file_reader = &TestFileReader::from(map);
+
+        let actual_chapter_content =
+            replace_template(start_chapter_content, file_reader, "", "", 0);
+
+        assert_eq!(actual_chapter_content, end_chapter_content);
+    }
+
+    #[test]
+    fn test_happy_path_with_default_values() {
+        let start_chapter_content = "{{#template footer.md}}";
+        let end_chapter_content = "Designed By - Goudham";
+        let file_name = PathBuf::from("footer.md");
+        let template_file_contents = "Designed By - {{$authors Goudham}}".to_string();
+        let map = HashMap::from([(file_name, template_file_contents)]);
+        let file_reader = &TestFileReader::from(map);
+
+        let actual_chapter_content =
+            replace_template(start_chapter_content, file_reader, "", "", 0);
+
+        assert_eq!(actual_chapter_content, end_chapter_content);
+    }
+
+    #[test]
+    fn test_happy_path_with_overridden_default_values() {
+        let start_chapter_content = "{{#template footer.md authors=Hazel}}";
+        let end_chapter_content = "Designed By - Hazel";
+        let file_name = PathBuf::from("footer.md");
+        let template_file_contents = "Designed By - {{$authors Goudham}}".to_string();
+        let map = HashMap::from([(file_name, template_file_contents)]);
+        let file_reader = &TestFileReader::from(map);
+
+        let actual_chapter_content =
+            replace_template(start_chapter_content, file_reader, "", "", 0);
+
+        assert_eq!(actual_chapter_content, end_chapter_content);
+    }
+
+    #[test]
+    fn test_happy_path_nested() {
+        let start_chapter_content = r"
+        {{#template header.md title=Example Title}}
+        Some content...";
+        let end_chapter_content = r"
+        # Example Title
+        <img src='example.png' alt='Example Title'>
+        Some content...";
+        let header_file_name = PathBuf::from("header.md");
+        let header_contents = r"# {{$title}}
+        {{#template image.md}}"
+            .to_string();
+        let image_file_name = PathBuf::from("image.md");
+        let image_contents = r"<img src='example.png' alt='Example Title'>".to_string();
+        let map = HashMap::from([
+            (image_file_name, image_contents),
+            (header_file_name, header_contents),
+        ]);
+        let file_reader = &TestFileReader::from(map);
+
+        let actual_chapter_content =
+            replace_template(start_chapter_content, file_reader, "", "", 0);
+
+        assert_eq!(actual_chapter_content, end_chapter_content);
+    }
 }
\ No newline at end of file
diff --git a/src/links.rs b/src/links.rs
index d780f38..996f6fe 100644
--- a/src/links.rs
+++ b/src/links.rs
@@ -1,12 +1,12 @@
-use std::collections::{HashMap, VecDeque};
-use std::fs;
+use std::collections::HashMap;
 use std::path::{Path, PathBuf};
 
-use anyhow::Context;
 use fancy_regex::{CaptureMatches, Captures, Regex};
 use lazy_static::lazy_static;
 use mdbook::errors::Result;
 
+use crate::FileReader;
+
 const ESCAPE_CHAR: char = '\\';
 const LINE_BREAKS: &[char] = &['\n', '\r'];
 
@@ -14,7 +14,7 @@ lazy_static! {
     // https://stackoverflow.com/questions/22871602/optimizing-regex-to-fine-key-value-pairs-space-delimited
     static ref TEMPLATE_ARGS: Regex = Regex::new(r"(?<=\s|\A)([^\s=]+)=(.*?)(?=(?:\s[^\s=]+=|$))").unwrap();
 
-    // r"(?x)\\\{\{\#.*\}\}|\{\{\s*\#(template)\s+([a-zA-Z0-9_^'<>().:*+|\\\/?-]+)\s+([^}]+)\}\}"
+    // r"(?x)\\\{\{\#.*\}\}|\{\{\s*\#(template)\s+([\S]+)\s*\}\}|\{\{\s*\#(template)\s+([\S]+)\s+([^}]+)\}\}"
     static ref TEMPLATE: Regex = Regex::new(
         r"(?x)                              # enable insignificant whitespace mode
          
@@ -22,12 +22,21 @@ lazy_static! {
         \#.*                                # match any character
         \}\}                                # escaped link closing parens
          
+        |                                   # or
+        
+        \{\{\s*                             # link opening parens and whitespace(s)
+        \#(template)                        # link type - template
+        \s+                                 # separating whitespace
+        ([\S]+)                             # relative path to template file
+        \s*                                 # optional separating whitespaces(s)
+        \}\}                                # link closing parens 
+        
         |                                   # or
          
         \{\{\s*                             # link opening parens and whitespace(s)
         \#(template)                        # link type - template
         \s+                                 # separating whitespace
-        ([\w'<>.:^\-\(\)\*\+\|\\\/\?]+)     # relative path to template file 
+        ([\S]+)                             # relative path to template file 
         \s+                                 # separating whitespace(s)
         ([^}]+)                             # get all template arguments
         \}\}                                # link closing parens"
@@ -73,67 +82,61 @@ impl<'a> Link<'a> {
     fn from_capture(cap: Captures<'a>) -> Option<Link<'a>> {
         let mut all_args = HashMap::with_capacity(20);
 
-        let link_type = match (cap.get(0), cap.get(1), cap.get(2), cap.get(3)) {
-            (Some(mat), _, _, _) if mat.as_str().contains(LINE_BREAKS) => {
-                /*
-                Given a template string that looks like:
-                {{#template
-                    footer.md
-                    path=../images
-                    author=Hazel
-                }}
-
-                The resulting args: <VecDeque<&str> will look like:
-                ["{{#template", "footer.md", "path=../images", "author=Hazel", "}}"]
-                 */
-                let mut args = mat
-                    .as_str()
-                    .lines()
-                    .map(|line| {
-                        line.trim_end_matches(LINE_BREAKS)
-                            .trim_start_matches(LINE_BREAKS)
-                    })
-                    .collect::<VecDeque<_>>();
-
-                // Remove {{#template
-                args.pop_front();
-                // Remove ending }}
-                args.pop_back();
-                // Store relative path of template file
-                let file = args.pop_front().unwrap();
-
-                let split_args = args
-                    .into_iter()
-                    .map(|arg| {
-                        let mut split_n = arg.splitn(2, '=');
-                        let key = split_n.next().unwrap().trim();
-                        let value = split_n.next().unwrap();
-                        (key, value)
-                    })
-                    .collect::<Vec<_>>();
-                all_args.extend(split_args);
-
-                Some(LinkType::Template(PathBuf::from(file.trim())))
-            }
-            (_, _, Some(file), Some(args)) => {
-                let matches = TEMPLATE_ARGS.captures_iter(args.as_str());
-
-                let split_args = matches
-                    .into_iter()
-                    .map(|mat| {
-                        let mut split_n = mat.unwrap().get(0).unwrap().as_str().splitn(2, '=');
-                        let key = split_n.next().unwrap().trim();
-                        let value = split_n.next().unwrap();
-                        (key, value)
-                    })
-                    .collect::<Vec<_>>();
-                all_args.extend(split_args);
-
+        // https://regex101.com/r/OBywLv/1
+        let link_type = match (
+            cap.get(0),
+            cap.get(1),
+            cap.get(2),
+            cap.get(3),
+            cap.get(4),
+            cap.get(5),
+        ) {
+            // This looks like {{#template <file>}}
+            (_, _, Some(file), None, None, None) => {
                 Some(LinkType::Template(PathBuf::from(file.as_str())))
             }
-            (Some(mat), _, _, _) if mat.as_str().starts_with(ESCAPE_CHAR) => {
+            // This looks like \{{#<whatever string>}}
+            (Some(mat), _, _, _, _, _) if mat.as_str().starts_with(ESCAPE_CHAR) => {
                 Some(LinkType::Escaped)
             }
+            (_, None, None, _, Some(file), Some(args)) => {
+                let split_args = match args.as_str().contains(LINE_BREAKS) {
+                    /*
+                    This looks like
+                       {{#template
+                           <file>
+                           <args>
+                       }}
+                    */
+                    true => args
+                        .as_str()
+                        .split(LINE_BREAKS)
+                        .map(|str| str.trim())
+                        .filter(|trimmed| !trimmed.is_empty())
+                        .map(|mat| {
+                            let mut split_n = mat.splitn(2, '=');
+                            let key = split_n.next().unwrap().trim();
+                            let value = split_n.next().unwrap();
+                            (key, value)
+                        })
+                        .collect::<Vec<_>>(),
+
+                    // This looks like {{#template <file> <args>}}
+                    false => TEMPLATE_ARGS
+                        .captures_iter(args.as_str())
+                        .into_iter()
+                        .map(|mat| {
+                            let mut split_n = mat.unwrap().get(0).unwrap().as_str().splitn(2, '=');
+                            let key = split_n.next().unwrap().trim();
+                            let value = split_n.next().unwrap();
+                            (key, value)
+                        })
+                        .collect::<Vec<_>>(),
+                };
+
+                all_args.extend(split_args);
+                Some(LinkType::Template(PathBuf::from(file.as_str())))
+            }
             _ => None,
         };
 
@@ -148,20 +151,16 @@ impl<'a> Link<'a> {
         })
     }
 
-    pub(crate) fn replace_args<P: AsRef<Path>>(&self, base: P) -> Result<String> {
+    pub(crate) fn replace_args<P, FR>(&self, base: P, file_reader: &FR) -> Result<String>
+    where
+        P: AsRef<Path>,
+        FR: FileReader,
+    {
         match self.link_type {
             LinkType::Escaped => Ok((&self.link_text[1..]).to_owned()),
             LinkType::Template(ref pat) => {
                 let target = base.as_ref().join(pat);
-
-                let contents = fs::read_to_string(&target).with_context(|| {
-                    format!(
-                        "Could not read template file {} ({})",
-                        self.link_text,
-                        target.display(),
-                    )
-                })?;
-
+                let contents = file_reader.read_to_string(&target, self.link_text)?;
                 Ok(Args::replace(contents.as_str(), &self.args))
             }
         }
@@ -245,11 +244,15 @@ impl<'a> Args<'a> {
     }
 
     fn from_capture(cap: Captures<'a>) -> Option<Args<'a>> {
+        // https://regex101.com/r/lKSOOl/3
         let arg_type = match (cap.get(0), cap.get(1), cap.get(2), cap.get(3)) {
+            // This looks like {{$path}}
             (_, Some(argument), None, None) => Some(ArgsType::Plain(argument.as_str())),
+            // This looks like {{$path ../images}}
             (_, _, Some(argument), Some(default_value)) => {
                 Some(ArgsType::Default(argument.as_str(), default_value.as_str()))
             }
+            // This looks like \{{$any string}}
             (Some(mat), _, _, _) if mat.as_str().starts_with(ESCAPE_CHAR) => {
                 Some(ArgsType::Escaped)
             }
@@ -299,22 +302,6 @@ mod link_tests {
     use std::path::PathBuf;
 
     use crate::links::{extract_args, extract_template_links, Args, ArgsType, Link, LinkType};
-    use crate::replace_template;
-
-    #[test]
-    fn test_escaped_template_link() {
-        let start = r"
-        Example Text
-        ```hbs
-        \{{#template template.md}} << an escaped link!
-        ```";
-        let end = r"
-        Example Text
-        ```hbs
-        {{#template template.md}} << an escaped link!
-        ```";
-        assert_eq!(replace_template(start, "", "", 0), end);
-    }
 
     #[test]
     fn test_extract_zero_template_links() {
@@ -322,12 +309,6 @@ mod link_tests {
         assert_eq!(extract_template_links(s).collect::<Vec<_>>(), vec![])
     }
 
-    #[test]
-    fn test_extract_zero_template_links_without_args() {
-        let s = "{{#template templates/footer.md}}";
-        assert_eq!(extract_template_links(s).collect::<Vec<_>>(), vec![])
-    }
-
     #[test]
     fn test_extract_template_links_partial_match() {
         let s = "Some random text with {{#template...";
@@ -342,7 +323,7 @@ mod link_tests {
 
     #[test]
     fn test_extract_template_links_empty() {
-        let s = "Some random text with {{#template}} and {{#template  }} {{}} {{#}}...";
+        let s = "Some random text with {{}} {{#}}...";
         assert_eq!(extract_template_links(s).collect::<Vec<_>>(), vec![]);
     }
 
@@ -352,6 +333,24 @@ mod link_tests {
         assert!(extract_template_links(s).collect::<Vec<_>>() == vec![]);
     }
 
+    #[test]
+    fn test_extract_zero_template_links_without_args() {
+        let s = "{{#template templates/footer.md}}";
+
+        let res = extract_template_links(s).collect::<Vec<_>>();
+
+        assert_eq!(
+            res,
+            vec![Link {
+                start_index: 0,
+                end_index: 33,
+                link_type: LinkType::Template(PathBuf::from("templates/footer.md")),
+                link_text: "{{#template templates/footer.md}}",
+                args: HashMap::new()
+            },]
+        );
+    }
+
     #[test]
     fn test_extract_template_links_simple() {
         let s =
@@ -361,13 +360,22 @@ mod link_tests {
 
         assert_eq!(
             res,
-            vec![Link {
-                start_index: 48,
-                end_index: 79,
-                link_type: LinkType::Template(PathBuf::from("test.rs")),
-                link_text: "{{#template test.rs lang=rust}}",
-                args: HashMap::from([("lang", "rust")])
-            },]
+            vec![
+                Link {
+                    start_index: 22,
+                    end_index: 43,
+                    link_type: LinkType::Template(PathBuf::from("file.rs")),
+                    link_text: "{{#template file.rs}}",
+                    args: HashMap::new()
+                },
+                Link {
+                    start_index: 48,
+                    end_index: 79,
+                    link_type: LinkType::Template(PathBuf::from("test.rs")),
+                    link_text: "{{#template test.rs lang=rust}}",
+                    args: HashMap::from([("lang", "rust")])
+                },
+            ]
         );
     }
 
@@ -489,6 +497,26 @@ year=2022
         );
     }
 
+    #[test]
+    fn test_extract_template_links_with_newlines_malformed() {
+        let s = "{{#template test.rs 
+        lang=rust
+        year=2022}}";
+
+        let res = extract_template_links(s).collect::<Vec<_>>();
+
+        assert_eq!(
+            res,
+            vec![Link {
+                start_index: 0,
+                end_index: 58,
+                link_type: LinkType::Template(PathBuf::from("test.rs")),
+                link_text: "{{#template test.rs \n        lang=rust\n        year=2022}}",
+                args: HashMap::from([("lang", "rust"), ("year", "2022")]),
+            },]
+        );
+    }
+
     #[test]
     fn test_extract_zero_args() {
         let s = "This is some text without any template links";