Implement OpenFile command

core/src/editor_buffer/mod.rs

@@ -2,8 +2,8 @@ use std::path::PathBuf;
 
 use crate::{Point, TextBuffer};
 
-mod io;
 mod command;
+mod io;
 pub use command::{Command, Movement, Unit};
 
 #[derive(Default)]
@@ -64,3 +64,47 @@ impl EditorBuffer {
         todo!()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use std::io::{Read, Seek, SeekFrom, Write};
+    use tempfile::NamedTempFile;
+
+    fn create_simple_test_file() -> NamedTempFile {
+        let inner = || {
+            let mut file = NamedTempFile::new()?;
+            writeln!(file, "Messe ocus Pangur Bán,")?;
+            writeln!(file, "cechtar nathar fria saindan")?;
+            writeln!(file, "bíth a menmasam fri seilgg")?;
+            writeln!(file, "mu menma céin im saincheirdd.")?;
+            writeln!(file)?;
+            writeln!(file, "Caraimse fos ferr cach clú")?;
+            writeln!(file, "oc mu lebran leir ingn")?;
+            writeln!(file, "ni foirmtech frimm Pangur Bá")?;
+            writeln!(file, "caraid cesin a maccdán.")?;
+            writeln!(file)?;
+            writeln!(file, "Orubiam scél cen scís")?;
+            writeln!(file, "innar tegdais ar noendís")?;
+            writeln!(file, "taithiunn dichrichide clius")?;
+            writeln!(file, "ni fristarddam arnáthius.")?;
+            file.seek(SeekFrom::Start(0))?;
+            Ok::<_, std::io::Error>(file)
+        };
+        inner().expect("Creating temporary file")
+    }
+
+    #[test]
+    fn open_file_loads_file_contents() {
+        let mut test_file = create_simple_test_file();
+        let mut expected_contents = String::new();
+        test_file
+            .read_to_string(&mut expected_contents)
+            .expect("Reading text file");
+        let mut target = EditorBuffer::new();
+        target.execute(Command::OpenFile(test_file.path().into()));
+        let found_contents: String = target.buffer.iter_chars().collect();
+        assert_eq!(expected_contents, found_contents);
+    }
+}