Make Component serialization deterministic, add integration tests

Just swap HashMap for BTreeMap, which has defined iteration order (also
organizes elements by key ordering, rather than hash -- strings support
both).

This allows us to write integration tests, so here they are.

Fixes #7.

2 files changed, 47 insertions, 6 deletions

diff --git a/src/components.rs b/src/components.rs
index d8f6c8e..b4efb91 100644
--- a/src/components.rs
+++ b/src/components.rs
@@ -4,7 +4,7 @@ use uuid::Uuid;
 // use std::io;
 use std::fmt;
 use std::mem;
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 
 use crate::properties::*;
 
@@ -18,7 +18,7 @@ pub struct Todo { inner: InnerComponent }
 
 #[derive(Debug, Default)]
 struct InnerComponent{
-    properties: HashMap<String,Property>,
+    properties: BTreeMap<String, Property>,
     multi_properties: Vec<Property>
 }
 
@@ -27,7 +27,7 @@ impl InnerComponent {
     /// copies over everything
     pub fn done(&mut self) -> Self {
         InnerComponent{
-            properties: mem::replace(&mut self.properties, HashMap::new()),
+            properties: mem::replace(&mut self.properties, BTreeMap::new()),
             multi_properties: mem::replace(&mut self.multi_properties, Vec::new()),
         }
     }
@@ -116,8 +116,8 @@ pub trait Component {
     /// These are used in the `BEGIN` and `END` line of the component.
     fn component_kind() -> &'static str;
 
-    /// Allows access to the inner properties HashMap.
-    fn properties(&self) -> &HashMap<String,Property>;
+    /// Allows access to the inner properties map.
+    fn properties(&self) -> &BTreeMap<String,Property>;
 
     /// Read-only access to `multi_properties`
     fn multi_properties(&self) -> &Vec<Property> ;
@@ -290,7 +290,7 @@ macro_rules! component_impl {
                 fn component_kind() -> &'static str { $kind }
 
                 /// Read-only access to `properties`
-                fn properties(&self) -> &HashMap<String, Property> {
+                fn properties(&self) -> &BTreeMap<String, Property> {
                     &self.inner.properties
                 }
 
diff --git a/tests/calendar.rs b/tests/calendar.rs
new file mode 100644
index 0000000..785bec5
--- /dev/null
+++ b/tests/calendar.rs
@@ -0,0 +1,41 @@
+use chrono::prelude::*;
+use icalendar::{Calendar, Class, Component, Event, EventStatus};
+
+const EXPECTED_CAL_CONTENT: &str = "\
+BEGIN:VCALENDAR\r
+VERSION:2.0\r
+PRODID:ICALENDAR-RS\r
+CALSCALE:GREGORIAN\r
+BEGIN:VEVENT\r
+CLASS:CONFIDENTIAL\r
+DESCRIPTION:Description\r
+DTEND:20140709T091011\r
+DTSTAMP:20190307T181159\r
+DTSTART:20140708T091011\r
+LOCATION:Somewhere\r
+PRIORITY:10\r
+STATUS:TENTATIVE\r
+SUMMARY:summary\r
+UID:euid\r
+END:VEVENT\r
+END:VCALENDAR\r
+";
+
+#[test]
+fn test_calendar_to_string() {
+    let mut calendar = Calendar::new();
+    let event = Event::new()
+        .status(EventStatus::Tentative)
+        .starts(Local.ymd(2014, 7, 8).and_hms(9, 10, 11))
+        .ends(Local.ymd(2014, 7, 9).and_hms(9, 10, 11))
+        .priority(11) // converted to 10
+        .summary("summary")
+        .description("Description")
+        .location("Somewhere")
+        .uid("euid")
+        .class(Class::Confidential)
+        .add_property("DTSTAMP", "20190307T181159")
+        .done();
+    calendar.push(event);
+    assert_eq!(calendar.to_string(), EXPECTED_CAL_CONTENT);
+}