diff --git a/js/id/geo.js b/js/id/geo.js
index 2137cdc35..7f3eb9457 100644
--- a/js/id/geo.js
+++ b/js/id/geo.js
@@ -118,7 +118,7 @@ iD.geo.lineIntersection = function(a, b) {
     }
 
     return null;
-}
+};
 
 // Return whether point is contained in polygon.
 //
diff --git a/test/spec/geo.js b/test/spec/geo.js
index a6a86ecb2..289bb8911 100644
--- a/test/spec/geo.js
+++ b/test/spec/geo.js
@@ -156,6 +156,34 @@ describe('iD.geo', function() {
         });
     });
 
+    describe('.lineIntersection', function() {
+        it('returns null if lines are colinear with overlap', function() {
+            var a = [[0, 0], [10, 0]],
+                b = [[-5, 0], [5, 0]];
+            expect(iD.geo.lineIntersection(a, b)).to.be.null;
+        });
+        it('returns null if lines are colinear but disjoint', function() {
+            var a = [[5, 0], [10, 0]],
+                b = [[-10, 0], [-5, 0]];
+            expect(iD.geo.lineIntersection(a, b)).to.be.null;
+        });
+        it('returns null if lines are parallel', function() {
+            var a = [[0, 0], [10, 0]],
+                b = [[0, 5], [10, 5]];
+            expect(iD.geo.lineIntersection(a, b)).to.be.null;
+        });
+        it('returns the intersection point between 2 lines', function() {
+            var a = [[0, 0], [10, 0]],
+                b = [[5, 10], [5, -10]];
+            expect(iD.geo.lineIntersection(a, b)).to.eql([5, 0]);
+        });
+        it('returns null if lines are not parallel but not intersecting', function() {
+            var a = [[0, 0], [10, 0]],
+                b = [[-5, 10], [-5, -10]];
+            expect(iD.geo.lineIntersection(a, b)).to.be.null;
+        });
+    });
+
     describe('.pointInPolygon', function() {
         it('says a point in a polygon is on a polygon', function() {
             var poly = [[0, 0], [0, 1], [1, 1], [1, 0], [0, 0]];
diff --git a/test/spec/svg/midpoints.js b/test/spec/svg/midpoints.js
index 499e9405b..55634d170 100644
--- a/test/spec/svg/midpoints.js
+++ b/test/spec/svg/midpoints.js
@@ -10,7 +10,7 @@ describe("iD.svg.Midpoints", function () {
             .call(iD.svg.Surface(context));
     });
 
-    it("finds the location of the midpoints", function () {
+    it("creates midpoint on segment completely within the extent", function () {
         var a = iD.Node({loc: [0, 0]}),
             b = iD.Node({loc: [50, 0]}),
             line = iD.Way({nodes: [a.id, b.id]}),
@@ -23,7 +23,7 @@ describe("iD.svg.Midpoints", function () {
         expect(surface.select('.midpoint').datum().loc).to.eql([25, 0]);
     });
 
-    it("doesn't create midpoints on segments with pixel length less than 40", function () {
+    it("doesn't create midpoint on segment with pixel length less than 40", function () {
         var a = iD.Node({loc: [0, 0]}),
             b = iD.Node({loc: [39, 0]}),
             line = iD.Way({nodes: [a.id, b.id]}),
@@ -35,4 +35,44 @@ describe("iD.svg.Midpoints", function () {
 
         expect(surface.selectAll('.midpoint')[0]).to.have.length(0);
     });
+
+    it("doesn't create midpoint on segment completely outside of the extent", function () {
+        var a = iD.Node({loc: [-100, 0]}),
+            b = iD.Node({loc: [-50, 0]}),
+            line = iD.Way({nodes: [a.id, b.id]}),
+            graph = iD.Graph([a, b, line]),
+            extent = iD.geo.Extent([0, 0], [100, 100]);
+
+        context.selectedIDs = function() { return [line.id]; };
+        surface.call(iD.svg.Midpoints(projection, context), graph, [line], filter, extent);
+
+        expect(surface.selectAll('.midpoint')[0]).to.have.length(0);
+    });
+
+    it("creates midpoint on extent edge for segment partially outside of the extent", function () {
+        var a = iD.Node({loc: [50, 0]}),
+            b = iD.Node({loc: [500, 0]}),
+            line = iD.Way({nodes: [a.id, b.id]}),
+            graph = iD.Graph([a, b, line]),
+            extent = iD.geo.Extent([0, 0], [100, 100]);
+
+        context.selectedIDs = function() { return [line.id]; };
+        surface.call(iD.svg.Midpoints(projection, context), graph, [line], filter, extent);
+
+        expect(surface.select('.midpoint').datum().loc).to.eql([100, 0]);
+    });
+
+    it("doesn't create midpoint on extent edge for segment with pixel length less than 20", function () {
+        var a = iD.Node({loc: [81, 0]}),
+            b = iD.Node({loc: [500, 0]}),
+            line = iD.Way({nodes: [a.id, b.id]}),
+            graph = iD.Graph([a, b, line]),
+            extent = iD.geo.Extent([0, 0], [100, 100]);
+
+        context.selectedIDs = function() { return [line.id]; };
+        surface.call(iD.svg.Midpoints(projection, context), graph, [line], filter, extent);
+
+        expect(surface.selectAll('.midpoint')[0]).to.have.length(0);
+    });
+
 });