diff --git a/src/main.rs b/src/main.rs
index b4feb2a42..85f09a23e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,6 +3,7 @@ mod intervals;
 mod lines;
 mod parse;
 mod positions;
+mod side_by_side;
 mod style;
 mod syntax;
 use clap::{App, AppSettings, Arg};
@@ -12,12 +13,8 @@ use std::path::Path;
 use typed_arena::Arena;
 
 use crate::dijkstra::mark_syntax;
-use crate::lines::{
-    apply_groups, enforce_length, format_line_num, join_overlapping, lhs_printable_width,
-    rhs_printable_width, visible_groups, MaxLine,
-};
+use crate::lines::{join_overlapping, visible_groups, MaxLine};
 use crate::parse::{find_lang, parse, parse_lines, ConfigDir};
-use crate::style::apply_colors;
 use crate::syntax::{change_positions, init_info, matching_lines};
 
 fn read_or_die(path: &str) -> Vec<u8> {
@@ -40,10 +37,6 @@ fn read_or_die(path: &str) -> Vec<u8> {
     }
 }
 
-fn term_width() -> Option<usize> {
-    term_size::dimensions().map(|(w, _)| w)
-}
-
 /// Do these bytes look like a binary (non-textual) format?
 fn is_probably_binary(bytes: &[u8]) -> bool {
     // If more than 20 of the first 1,000 characters are not valid
@@ -116,8 +109,6 @@ fn main() {
         .to_string()
         .replace("\t", "    ");
 
-    let terminal_width = term_width().unwrap_or(80);
-
     let arena = Arena::new();
 
     let (lhs, rhs) = match &lang {
@@ -149,38 +140,15 @@ fn main() {
     }
     groups = join_overlapping(groups);
 
-    let lhs_column_width = format_line_num(groups.last().unwrap().max_visible_lhs().0).len();
-    let rhs_column_width = format_line_num(groups.last().unwrap().max_visible_rhs().0).len();
-
-    let lhs_formatted_length =
-        lhs_printable_width(&lhs_src, &groups, lhs_column_width, terminal_width);
-    let rhs_formatted_length = rhs_printable_width(
-        &rhs_src,
-        &groups,
-        lhs_formatted_length,
-        rhs_column_width,
-        terminal_width,
-    );
-
-    let lhs_content_width = lhs_formatted_length - lhs_column_width;
-    let rhs_content_width = rhs_formatted_length - rhs_column_width;
-
-    let lhs_src = enforce_length(&lhs_src, lhs_content_width);
-    let rhs_src = enforce_length(&rhs_src, rhs_content_width);
-    let lhs_colored = apply_colors(&lhs_src, true, &lhs_positions);
-    let rhs_colored = apply_colors(&rhs_src, false, &rhs_positions);
-
     print!(
         "{}",
-        apply_groups(
-            &lhs_colored,
-            &rhs_colored,
-            &groups,
+        side_by_side::display(
+            &lhs_src,
+            &rhs_src,
+            &lhs_positions,
+            &rhs_positions,
             &lhs_matched_lines,
-            lhs_content_width,
-            rhs_content_width,
-            lhs_column_width,
-            rhs_column_width,
+            &groups
         )
     );
     println!();
diff --git a/src/side_by_side.rs b/src/side_by_side.rs
new file mode 100644
index 000000000..db8e9ecc6
--- /dev/null
+++ b/src/side_by_side.rs
@@ -0,0 +1,55 @@
+use std::collections::HashMap;
+
+use crate::lines::{
+    apply_groups, enforce_length, format_line_num, lhs_printable_width, rhs_printable_width,
+    LineGroup, LineNumber,
+};
+use crate::style::apply_colors;
+use crate::syntax::MatchedPos;
+
+fn term_width() -> Option<usize> {
+    term_size::dimensions().map(|(w, _)| w)
+}
+
+pub fn display(
+    lhs_src: &str,
+    rhs_src: &str,
+    lhs_positions: &[MatchedPos],
+    rhs_positions: &[MatchedPos],
+    lhs_matched_lines: &HashMap<LineNumber, LineNumber>,
+    groups: &[LineGroup],
+) -> String {
+    let lhs_column_width = format_line_num(groups.last().unwrap().max_visible_lhs().0).len();
+    let rhs_column_width = format_line_num(groups.last().unwrap().max_visible_rhs().0).len();
+
+    let terminal_width = term_width().unwrap_or(80);
+
+    let lhs_formatted_length =
+        lhs_printable_width(lhs_src, groups, lhs_column_width, terminal_width);
+    let rhs_formatted_length = rhs_printable_width(
+        rhs_src,
+        groups,
+        lhs_formatted_length,
+        rhs_column_width,
+        terminal_width,
+    );
+
+    let lhs_content_width = lhs_formatted_length - lhs_column_width;
+    let rhs_content_width = rhs_formatted_length - rhs_column_width;
+
+    let lhs_src = enforce_length(lhs_src, lhs_content_width);
+    let rhs_src = enforce_length(rhs_src, rhs_content_width);
+    let lhs_colored = apply_colors(&lhs_src, true, lhs_positions);
+    let rhs_colored = apply_colors(&rhs_src, false, rhs_positions);
+
+    apply_groups(
+        &lhs_colored,
+        &rhs_colored,
+        groups,
+        lhs_matched_lines,
+        lhs_content_width,
+        rhs_content_width,
+        lhs_column_width,
+        rhs_column_width,
+    )
+}