#57 Fixed ambigious branch coveragae

Author: sksamuel

src/main/scala/scoverage/coverage.scala

@@ -128,7 +128,21 @@ trait CoverageMetrics {
   def branchCoveragePercent = branchCoverage * 100
   def invokedBranches: Iterable[MeasuredStatement] = branches.filter(_.count > 0)
   def invokedBranchesCount = invokedBranches.size
-  def branchCoverage: Double = if (branchCount == 0) 1 else invokedBranchesCount / branchCount.toDouble
+
+  /**
+   * @see http://stackoverflow.com/questions/25184716/scoverage-ambiguous-measurement-from-branch-coverage
+   */
+  def branchCoverage: Double = {
+    // if there are zero branches, then we have a single line of execution.
+    // in that case, if there is at least some coverage, we have covered the branch.
+    // if there is no coverage then we have not covered the branch
+    if (branchCount == 0) {
+      if (statementCoverage > 0) 1
+      else 0
+    } else {
+      invokedBranchesCount / branchCount.toDouble
+    }
+  }
   def branchCoverageFormatted: String = "%.2f".format(branchCoveragePercent)
 }
 

src/test/scala/scoverage/CoverageMetricsTest.scala

@@ -0,0 +1,42 @@
+package scoverage
+
+import org.scalatest.{FreeSpec, Matchers}
+
+class CoverageMetricsTest extends FreeSpec with Matchers {
+
+  "no branches with at least one invoked statement should have 100% branch coverage" in {
+    val metrics = new CoverageMetrics {
+      override def statements: Iterable[MeasuredStatement] = Seq(MeasuredStatement(null,
+        null,
+        0,
+        0,
+        0,
+        0,
+        null,
+        null,
+        null,
+        false,
+        1))
+    }
+    metrics.branchCount shouldBe 0
+    metrics.branchCoverage - 1 shouldBe < (0.0001)
+  }
+
+  "no branches with no invoked statements should have 0% branch coverage" in {
+    val metrics = new CoverageMetrics {
+      override def statements: Iterable[MeasuredStatement] = Seq(MeasuredStatement(null,
+        null,
+        0,
+        0,
+        0,
+        0,
+        null,
+        null,
+        null,
+        false,
+        0))
+    }
+    metrics.branchCount shouldBe 0
+    metrics.branchCoverage shouldBe 0
+  }
+}